Document:

Employee Stock Purchase Plan

 Exhibit 10.18 
 PROTO LABS, INC. 
 EMPLOYEE STOCK PURCHASE PLAN 

 

	1.	Purpose of the Plan. The purpose of this Proto Labs, Inc. Employee Stock Purchase Plan (the “Plan”) is to provide the employees of Proto Labs, Inc.
(the “Company”) and its participating subsidiaries with a convenient means of purchasing shares of the Company’s common stock from time to time at a discount to market prices through the use of payroll deductions. The Company intends
that the Plan shall qualify as an “employee stock purchase plan” under Section 423 of the Code. 

  

	2.	Definitions. The terms defined in this section are used (and capitalized) elsewhere in this Plan. 

 

	 	2.1.	“Affiliate” means each domestic or foreign entity that is a “parent corporation” or “subsidiary corporation” of the Company,
as defined in Code Sections 424(e) and 424(f) or any successor provisions. 

  

	 	2.2	“Board” means the Board of Directors of the Company. 

 

	 	2.3	“Code” means the Internal Revenue Code of 1986, as amended from time to time, and the regulations promulgated thereunder.

  

	 	2.4	“Committee” means the Compensation Committee of the Board or such other committee of non-employee directors appointed by the Board to administer
the Plan as provided in Section 13. 

  

	 	2.5	“Common Stock” means the common stock, par value $0.001 per share, of the Company. 

 

	 	2.6	“Company” means Proto Labs, Inc., a Minnesota corporation. 

 

	 	2.7	“Corporate Transaction” means (i) a merger, consolidation or statutory share exchange in which the Company is not the surviving corporation
(other than a merger or consolidation with a wholly owned subsidiary, a reincorporation of the Company in a different jurisdiction, or other such transaction in which the shareholders of the Company immediately prior to such transaction own more
than 50% of the combined voting power of the voting stock of the surviving or successor corporation (or its parent corporation) and the rights to purchase Shares granted under this Plan are assumed, converted or replaced by the surviving or
successor corporation, which assumption will be binding on all Participants), (ii) a merger or statutory share exchange in which the Company is the surviving corporation but after which the shareholders of the Company immediately prior to such
transaction (other than any shareholder which combines (or which owns or controls another corporation which combines) with the Company in such a transaction) cease to own more than 50% of the combined voting power of the Company’s voting stock,
or (iii) the sale of substantially all of the assets of the Company. 

  

	 	2.8	“Designated Affiliate” means any Affiliate which has been expressly designated by the Board or Committee as a corporation whose Eligible
Employees may participate in the Plan. 

  

	 	2.9	“Eligible Compensation” means the gross cash compensation (including wages, salary, commission, bonus, and overtime earnings) paid by the
Company or any Affiliate to a Participant in accordance with the Participant’s terms of employment, but shall not include any employer contributions to a 401(k) or other retirement plan, stock option gains or other any amount included in income
with respect to equity-based incentive awards, or any similar extraordinary remuneration received by such Participant. 

	 	2.10	“Eligible Employee” means any employee of the Company or a Designated Affiliate, except for any employee who, immediately after a right to
purchase is granted under the Plan, would be deemed, for purposes of Code Section 423(b)(3), to own stock possessing 5% or more of the total combined voting power or value of all classes of stock of the Company or any Affiliate.

  

	 	2.11	“Exchange Act” means the Securities Exchange Act of 1934, as amended from time to time, and the regulations promulgated thereunder.

  

	 	2.12	“Fair Market Value” of a share of Common Stock as of any date means (i) if the Company’s Common Stock is then listed on a national
securities exchange, the closing price for a share of such Common Stock on such exchange on said date, or, if no sale has been made on such exchange on said date, on the last preceding day on which any sale shall have been made; (ii) if the
Company’s Common Stock is not then listed on a national securities exchange, such value as the Committee in its discretion may in good faith determine, provided that for any Offering that commences on the IPO Date, the Fair Market Value of the
shares of Common Stock on the first day of the applicable Purchase Period will be the price per share at which shares are first sold to the public in the Company’s initial public offering as specified in the final prospectus for that initial
public offering. The determination of Fair Market Value shall be subject to adjustment as provided in Section 14.1. 

  

	 	2.13	“IPO Date” means the date of the underwriting agreement between the Company and the underwriter(s) managing the initial public offering of the
Common Stock, pursuant to which the Common Stock is priced for the initial public offering. 

  

	 	2.14	“Offering” means the right provided to Participants to purchase Shares under the Plan with respect to a Purchase Period.

  

	 	2.15	“Participant” means an Eligible Employee who has elected to participate in the Plan in the manner set forth in Section 4 and whose
participation has not ended pursuant to Section 8.1 or Section 9. 

  

	 	2.16	“Plan” means this Proto Labs, Inc. Employee Stock Purchase Plan, as it may be amended from time to time. 

 

	 	2.17	“Purchase Date” means the last Trading Day of a Purchase Period. 

 

	 	2.18	“Purchase Period” means a period of six months beginning either (i) on May 16 of each calendar year and ending on the next
November 15, or (ii) on November 16 in each calendar year and ending on the next May 15, or such other period of time (but not to exceed 27 months or such longer period as may be permitted under Code Section 423) commencing
on such date as may be established by the Committee. 

  

	 	2.19	“Recordkeeping Account” means the account maintained in the books and records of the Company recording the amount contributed to the Plan by
each Participant through payroll deductions. 

  

	 	2.20	“Shares” means shares of Common Stock. 

  

	 	2.21	“Trading Day” means a day on which the national stock exchanges in the United States are open for trading. 

 

	3.	 Shares Available. Shares may be sold by the Company to Eligible Employees at any time after this Plan has been approved by the shareholders of
the Company, but not more than 1,500,000 Shares 

  
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(subject to adjustment as provided in Section 14.1) may be sold to Eligible Employees pursuant to this Plan. If the purchases by all Participants in an Offering would otherwise cause the
aggregate number of Shares to be sold under the Plan to exceed the number specified in this Section 3, each Participant in that Offering shall be allocated a ratable portion of the remaining number of Shares which may be sold under the Plan.

  

	4.	Eligibility and Participation. To be eligible to participate in the Plan for a given Purchase Period, an employee must be an Eligible Employee on the first day
of such Purchase Period. An Eligible Employee may elect to participate in the Plan by filing an election form with the Company before the first day of a Purchase Period that authorizes regular payroll deductions from Eligible Compensation beginning
with the first payday in such Purchase Period and continuing until the Plan is terminated or the Eligible Employee withdraws from the Plan, modifies his or her authorization, or ceases to be an Eligible Employee, as hereinafter provided.

  

	5.	Amount of Common Stock Each Eligible Employee May Purchase. 

  

	 	5.1.	Subject to the provisions of this Plan, each Participant shall be offered the right to purchase on the Purchase Date the maximum number of Shares (including fractional
Shares) that can be purchased with the entire balance in the Participant’s Recordkeeping Account at the per Share price specified in Section 5.2. Notwithstanding the foregoing, no Participant shall be entitled to: 

 

	 	(a)	the right to purchase Shares under this Plan and all other employee stock purchase plans (within the meaning of Code Section 423(b)), if any, of the Company and
its Affiliates that accrues at a rate which in the aggregate exceeds $25,000 of Fair Market Value (determined on the first day of a Purchase Period when the right is granted) for each calendar year in which such right is outstanding at any time; or

  

	 	(b)	purchase more than 1,250 Shares in any Offering under this Plan, such limit subject to adjustment from time to time as provided in Section 14.1.

  

	 	5.2.	Unless a greater purchase price is established by the Committee for an Offering prior to the commencement of the applicable Purchase Period, the purchase price of each
Share sold pursuant to this Plan will be the lesser of (i) 85% of the Fair Market Value of such Share on the first day of the applicable Purchase Period, or (ii) 85% of the Fair Market Value of such Share on the last day of the Purchase
Period. 

  

	6.	Method of Participation. 

  

	 	6.1.	The Company shall give notice to each Eligible Employee of the opportunity to purchase Shares pursuant to this Plan and the terms and conditions of such Offering. The
Company contemplates that for tax purposes the first day of a Purchase Period will be the date of the grant of the right to purchase such Shares. 

  

	 	6.2.	 Each Eligible Employee who desires to participate in the Plan for a Purchase Period shall signify his or her election to do so by signing and filing
with the Company an election form approved by the Committee. An Eligible Employee may elect to have any whole percent of Eligible Compensation (that is, 1%, 2%, 3%, etc.) withheld as a payroll deduction, but not exceeding 15% per pay period. An
election to participate in the Plan and to authorize payroll deductions as described herein must be made before the first day of a Purchase Period. The election shall be effective for the first payday in the Purchase Period immediately following the
filing of such election form and shall remain in effect until the Plan is terminated or such Participant withdraws from the Plan, modifies his or her authorization, or ceases to be an Eligible

  
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Employee, as hereinafter provided. If required under applicable law or if specifically provided in an Offering, in addition to or instead of making contributions by payroll deductions, a
Participant may make contributions through the payment by cash or check prior to a Purchase Date. A Participant may make additional payments into his or her account if specifically provided for in the Offering, and then only if the Participant has
not already had the maximum permitted amount withheld during the Offering through payroll deductions, subject to the limitations set forth in Section 5.1. 

 

	 	6.3.	Each Offering shall consist of a single Purchase Period and shall be in such form and shall contain such terms and conditions as the Committee shall deem appropriate,
consistent with the terms of the Plan. The Committee may provide for separate Offerings for different Designated Affiliates, and the terms and conditions of the separate Offerings, including the applicable Purchase Period, need not be consistent.
Any Offering shall comply with the requirement of Code Section 423 that all Participants shall have the same rights and privileges for such Offering. The terms and conditions of any Offering shall be incorporated by reference into the Plan and
treated as part of the Plan. 

  

	7.	Recordkeeping Account. 

  

	 	7.1.	The Company shall maintain a Recordkeeping Account for each Participant. Payroll deductions pursuant to Section 6 will be credited to such Recordkeeping Accounts
on each payday. 

  

	 	7.2.	No interest will be credited to a Participant’s Recordkeeping Account (unless required under local law). 

 

	 	7.3.	The Recordkeeping Account is established solely for accounting purposes, and all amounts credited to the Recordkeeping Account will remain part of the general assets of
the Company and need not be segregated from other corporate funds (unless required under local law). 

  

	 	7.4.	A Participant may not make any separate cash payment into a Recordkeeping Account, except as may be permitted by the Committee in accordance with Section 6.2.

  

	8.	Right to Adjust Participation; Withdrawals from Recordkeeping Account. 

 

	 	8.1.	A Participant may at any time withdraw from the Plan. If a Participant withdraws from the Plan, the Company will pay to the Participant in cash the entire balance in
such Participant’s Recordkeeping Account and no further deductions will be made from the Participant’s Eligible Compensation during such Purchase Period. A Participant who withdraws from the Plan will not be eligible to reenter the Plan
until the next succeeding Purchase Period, and any such reentry shall be through the enrollment process described in Section 6.2. 

  

	 	8.2.	Except for a withdrawal from the Plan as provided in Section 8.1, a Participant may not increase or decrease the deductions from his or her Eligible Compensation
during a Purchase Period. 

  

	 	8.3.	Notification of a Participant’s election to withdraw from the Plan and terminate deductions shall be made by signing and filing with the Company an appropriate
form approved by the Committee. The Committee may promulgate rules regarding the time and manner for providing any such written notice, which may include a requirement that the notice be on file with the Company’s designated office for a
reasonable period before it will be effective. 

  

	9.	 Termination of Employment. If the employment of a Participant is terminated for any reason, including death, disability, or retirement, the
entire balance in the Participant’s Recordkeeping Account will 

  
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be refunded in cash to the Participant within 30 days after the date of termination of employment. For purposes of the Plan, a Participant will not be deemed to have terminated employment while
the Participant is on sick leave, military leave or other leave of absence approved by the Company. Where the period of leave exceeds 90 days and the Participant’s right to reemployment is not guaranteed either by statute or by contract, the
employment relationship shall be deemed to have terminated on the ninety-first day of such leave. 

  

	10.	Purchase of Shares. 

  

	 	10.1.	As of the Purchase Date, the entire balance in each Participant’s Recordkeeping Account will be used to purchase the maximum number of Shares (including fractional
Shares) (subject to the limitations of Section 5.1) at the purchase price determined in accordance with Section 5.2, unless the Participant has filed an appropriate form with the Company in advance of that date to withdraw from the Plan in
accordance with Section 8.1. Any amount in a Participant’s Recordkeeping Account that, for any reason, is not used to purchase Shares pursuant to this Section 10.1 will be refunded to the Participant. 

 

	 	10.2.	In circumstances where payroll deductions have been taken from a Participant’s Eligible Compensation in a currency other than United States dollars, Shares shall
be purchased by converting the balance in the Participant’s Recordkeeping Account to United States dollars at the exchange rate in effect at the end of the fifth Trading Day preceding the Purchase Date, as published by Bloomberg.com if
available or otherwise as determined with respect to a particular jurisdiction by the Committee or its delegate for this purpose, and such dollar amount shall be used to purchase Shares as of the Purchase Date. 	 

  

	 	10.3.	Promptly after the end of each Purchase Period, a certificate for the number of Shares purchased by all Participants shall be issued and delivered to an agent selected
by the Company. The agent will hold such certificate for the benefit of all Participants who have purchased Shares and will maintain an account for each Participant reflecting the number of Shares (including fractional Shares) credited to the
account of each Participant. Each Participant will be entitled to direct the voting of all Shares credited to such Participant’s account by the agent. Each Participant may also direct such agent to sell such Shares and distribute the net
proceeds of such sale to the Participant. At any time after the Participant has satisfied the minimum holding period requirements established by Code Section 423(a)(1), a Participant may request from the agent a certificate representing the
whole Shares credited to the Participant’s account, in which case the agent shall transfer a certificate for such whole number of Shares directly to the Participant and will pay the Participant a cash amount representing the Fair Market Value
of any fractional Share. 	 

  

	11.	Rights as a Shareholder. A Participant shall not be entitled to any of the rights or privileges of a shareholder of the Company with respect to Shares, including
the right to vote or direct the voting or to receive any dividends that may be declared by the Company, until (i) the Participant actually has paid the purchase price for such Shares and (ii) certificates for such Shares have been issued
either to the agent or to the Participant, as provided in Section 10. 

  

	12.	Rights Not Transferable. A Participant’s rights under this Plan are exercisable only by the Participant during his or her lifetime, and may not be sold,
pledged, assigned, transferred or disposed of in any manner other than by will or the laws of descent and distribution. Any attempt to sell, pledge, assign, transfer or dispose of the same shall be null and void and without effect. The amounts
credited to a Recordkeeping Account may not be sold, pledged, assigned, transferred or disposed of in any way, and any attempted sale, pledge, assignment, transfer or other disposition of such amounts will be null and void and without effect.

  
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	13.	Administration of the Plan. 

  

	 	13.1.	This Plan shall be administered by the Committee. Subject to the express provisions of the Plan and applicable law, and in addition to other express powers and
authorizations conferred on the Committee by the Plan, the Committee shall have full power and authority to: 

  

	 	(a)	Determine when each Purchase Period under this Plan shall occur, and the terms and conditions of each related Offering (which need not be identical), including, for
purposes of the initial Offering, providing for automatic enrollment of Eligible Employees in the Plan and the ability of Eligible Employees to subsequently elect to make changes in the amount withheld as a payroll deduction;

  

	 	(b)	Designate from time to time which Affiliates of the Company shall be eligible to participate in the Plan; 

 

	 	(c)	Construe and interpret the Plan and establish, amend and revoke rules, regulations and procedures for the administration of the Plan. The Committee may, in the exercise
of this power, correct any defect, omission or inconsistency in the Plan, in such manner and to the extent it may deem necessary, desirable or appropriate to make the Plan fully effective; 

 

	 	(d)	Exercise such powers and perform such acts as the Committee may deem necessary, desirable or appropriate to promote the best interests of the Company and its Designated
Affiliates and to carry out the intent that the Offerings made under the Plan are treated as qualifying under Code Section 423(b); 

  

	 	(e)	As more fully described in Section 19, to adopt such rules, procedures and sub-plans as may be necessary, desirable or appropriate to permit participation in the
Plan by employees who are foreign nationals or employed outside the United States by a non-U.S. Designated Affiliate, and to achieve tax, securities law and other compliance objectives in particular locations outside the United States; and

  

	 	(f)	Adopt and amend as the Committee deems appropriate a Plan rule specifying that Shares purchased by a Participant during a Purchase Period may not be sold by the
Participant for a specified period of time after the Purchase Date on which the Shares were purchased by the Participant, and establish such procedures as the Committee may deem necessary to implement such rule. 

 

	 	13.2.	Unless otherwise expressly provided in the Plan, all designations, determinations, interpretations, and other decisions under or with respect to the Plan shall be
within the sole discretion of the Committee, may be made at any time and shall be final, conclusive, and binding upon all persons, including the Company, any Affiliate, any Participant and any Eligible Employee. 

 

	 	13.3.	Subject to the terms of the Plan and applicable law, the Committee may delegate ministerial duties associated with the administration of the Plan to such of the
Company’s officers, employees or agents as the Committee may determine. 

  

	 	13.4.	 No member of the Board or Committee shall be liable for any action taken or determination made in good faith with respect to the Plan. In addition to
such other rights of indemnification as they may have as members of the Board or officers or employees of the Company or a Designated Affiliate, members of the Board and Committee and any officers or employees of the

  
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Company or Designated Affiliate to whom authority to act for the Committee is delegated shall be indemnified by the Company from and against any and all liabilities, costs and expenses incurred
by such persons as a result of any act or omission to act in connection with the performance of such person’s duties, responsibilities and obligations under the Plan if such person has acted in good faith and in a manner that he or she
reasonably believes to be in, or not opposed to, the best interests of the Company. 

  

	14.	Adjustment upon Changes in Capitalization and Corporate Transactions. 

 

	 	14.1.	In the event of any change in the Common Stock of the Company by reason of a stock dividend, stock split, reverse stock split, corporate separation, recapitalization,
merger, consolidation, combination, exchange of shares and the like, the Committee shall make such equitable adjustments as it deems appropriate in the aggregate number and class of shares available under this Plan and the number, class and purchase
price of shares available but not yet purchased under this Plan. 

  

	 	14.2.	In the event of a Corporate Transaction, the Board may determine and provide that: (i) each right to acquire Shares on any Purchase Date that is scheduled to occur
after the date of the consummation of the Corporate Transaction shall be continued or assumed or an equivalent right shall be substituted by the surviving or successor corporation or a parent or subsidiary of such corporation; (ii) the Plan
shall be terminated; or (iii) the Purchase Period then in progress shall be shortened by setting a new Purchase Date. If a new Purchase Date is set, it shall be a specified date before the date of the consummation of the Corporate Transaction.
Each Participant shall be notified in writing, prior to any new Purchase Date, that the Purchase Date for the existing Offering has been changed to the new Purchase Date and that the Participant’s right to acquire Shares will be exercised
automatically on the new Purchase Date unless prior to such date the Participant’s employment has been terminated or the Participant has withdrawn from the Plan. 

 

	15.	Registration of Certificates. Stock certificates will be registered in the name of the Participant, or jointly in the name of the Participant and another person,
as the Participant may direct on an appropriate form filed with the Company or the agent. 

  

	16.	Amendment or Suspension of Plan. The Board may at any time suspend this Plan or amend it in any respect, but no such amendment may, without shareholder approval,
increase the number of shares reserved under this Plan, or effect any other change in the Plan that would require shareholder approval under applicable law or to maintain compliance with Code Section 423. No such amendment or suspension shall
adversely affect the rights of Participants pursuant to Shares previously acquired under the Plan. During any suspension of the Plan, no new Offering or Purchase Period shall begin and no Eligible Employee shall be offered any new right to purchase
Shares under the Plan or any opportunity to elect to participate in the Plan, and any existing payroll deduction authorizations shall be suspended, but any such right to purchase Shares previously granted for a Purchase Period that began prior to
the Plan suspension shall remain subject to the other provisions of this Plan and the discretion of the Board and the Committee with respect thereto. 

  

	17.	 Effective Date and Term of Plan. The Plan will become effective on the IPO Date. No rights to purchase Shares granted under this Plan will be
exercised unless and until the Plan has been approved by the shareholders of the Company, which approval must be within 12 months before or after the date the Plan is adopted by the Board of Directors. The Plan and all rights of Participants
hereunder shall terminate (i) at any time, at the discretion of the Board of Directors, or (ii) upon the completion of any Offering under which the limitation on the total number of shares to be issued set forth in Section 3 has been
reached. Except as otherwise determined by the Board, upon termination of this Plan, the Company shall pay to each 

  
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Participant cash in an amount equal to the entire remaining balance in such Participant’s Recordkeeping Account. 

 

	18.	Governmental Regulations and Listing. All rights granted or to be granted to Eligible Employees under this Plan are expressly subject to all applicable laws and
regulations and to the approval of all governmental authorities required in connection with the authorization, issuance, sale or transfer of the Shares reserved for this Plan, including, without limitation, there being a current registration
statement of the Company under the Securities Act of 1933, as amended, covering the Shares purchasable on the Purchase Date applicable to such Shares, and if such a registration statement shall not then be effective, the term of such Purchase Period
shall be extended until the first business day after the effective date of such a registration statement, or post-effective amendment thereto. If applicable, all such rights hereunder are also similarly subject to effectiveness of an appropriate
listing application to a national securities exchange covering the Shares issuable under the Plan upon official notice of issuance. 

  

	19.	Rules for Foreign Jurisdictions. The Committee may adopt rules, procedures or subplans relating to the operation and administration of the Plan to accommodate
the specific requirements of local laws and procedures. Without limiting the generality of the foregoing, the Committee is specifically authorized to adopt rules and procedures regarding handling of payroll deductions, payment of interest,
conversion of local currency, payroll tax, the definition of Eligible Compensation, withholding procedures and handling of stock certificates that vary with local requirements. 

 

	20.	Miscellaneous. 

  

	 	20.1.	This Plan shall not be deemed to constitute a contract of employment between the Company and any Participant, nor shall it interfere with the right of the Company to
terminate the employment of any Participant and treat him or her without regard to the effect that such treatment might have upon him or her under this Plan. 

 

	 	20.2.	Wherever appropriate as used herein, the masculine gender may be read as the feminine gender, the feminine gender may be read as the masculine gender, the singular may
be read as the plural and the plural may be read as the singular. 

  

	 	20.3.	This Plan, and all agreements hereunder, shall be construed in accordance with and governed by the laws of the State of Minnesota. 

 

	 	20.4.	Any reference in the Plan to election or enrollment forms, notices, authorizations or any other document to be provided in writing shall include any such form, notice,
authorization or document delivered electronically, including through the Company’s intranet, in accordance with procedures established by the Committee. 

 

	 	20.5.	Any reference in this Plan to the issuance or transfer of a stock certificate evidencing Shares shall be deemed to include, in the Committee’s discretion, the
issuance or transfer of such Shares in book-entry or electronic form. Uncertificated Shares shall be deemed delivered for all purposes of this Plan when the Company or its agent shall have provided to the recipient of the Shares a notice of issuance
or transfer by electronic mail (with proof of receipt) or by United States mail, and have recorded the issuance or transfer in its records. 

  
 8Amendment

 Exhibit 10.20 
 AMENDMENT 
 This Amendment (this “Amendment”), dated as of
February 10, 2012, amends and modifies the (i) Amended and Restated Investors’ Rights Agreement, dated July 19, 2011 (the “IRA”), by and among Proto Labs, Inc., a Minnesota corporation (the
“Company”), and each investor that is party thereto, (ii) Voting Agreement, dated August 1, 2008 and amended May 31, 2011 (the “Voting Agreement”), by and among the Company and each investor (a
“Voting Investor”) and key holder (a “Voting Key Holder”) that is party thereto, (iii) Right of First Refusal and Co-Sale Agreement, dated August 1, 2008 (the “ROFR and Co-Sale
Agreement”), by and among the Company and each investor (a “ROFR Investor”) and key holder (a “ROFR Key Holder”) that is party thereto. 

1. The undersigned, constituting the Company, North Bridge Growth Equity I, L.P., a Delaware limited partnership (“North
Bridge”), and Protomold Investment Company, LLC, a Minnesota limited liability company (“PIC”), hereby amend and restate Section 1.18 of the IRA in its entirety as follows: 

“1.18 “Qualified IPO” means the Company’s first firm-commitment underwritten public offering of
its Common Stock pursuant to an effective registration statement under the Securities Act (provided that if such a public offering is consummated on or after March 15, 2012, and before August 1, 2012, the offering price must be at least
$244.12 per share (subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization), resulting in at least $40,000,000 of aggregate gross proceeds to the Company; if such a public
offering is consummated before March 15, 2012, no minimum offering price or aggregate gross proceeds thresholds apply).” 
 2. The undersigned, constituting the Company, PIC, the Voting Key Holders (exclusive of PIC) holding a majority of the shares held by the Voting Key Holders, and the holders of a majority of the shares of
common stock issued or issuable upon conversion of the outstanding shares of Series A Preferred Stock held by the Voting Investors, hereby amend and restate Section 4 of the Voting Agreement in its entirety as follows: 

“4. Term. This Agreement shall be effective as of the date hereof and shall continue in effect until and shall
terminate upon the earliest to occur of (a) the consummation of the sale of shares of Common Stock to the public in a firm-commitment underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933,
as amended (provided that if such a public offering is consummated on or after March 15, 2012, and before August 1, 2012, the offering price shall be at least $244.12 per share (subject to appropriate adjustment in the event of any stock
dividend, stock split, combination or other similar recapitalization), resulting in at least $40,000,000 of aggregate gross proceeds to the Company; if such a public offering is consummated before March 15, 2012, no minimum offering price or
aggregate gross proceeds thresholds apply); and (b) termination of this Agreement in accordance with Section 5.8 below.” 

 3. The undersigned, constituting the Company, PIC, the ROFR Key Holders (exclusive of PIC)
holding a majority of the shares of Transfer Stock (as defined in the ROFR and Co-Sale Agreement) held by all of the ROFR Key Holders, and the holders of a majority of the shares of common stock issued or issuable upon conversion of the outstanding
shares of Series A Preferred Stock held by the ROFR Investors, hereby amend and restate Section 6.1 of the ROFR and Co-Sale Agreement in its entirety as follows: 

“6.1 Term. This Agreement shall automatically terminate upon the earlier of (a) except with respect to
Section 5 above, which shall continue as provided therein, immediately prior to the consummation of the sale of shares of Common Stock to the public in a firm-commitment underwritten public offering pursuant to an effective registration
statement under the Securities Act of 1933, as amended (provided that if such a public offering is consummated on or after March 15, 2012, and before August 1, 2012, the offering price shall be at least $244.12 per share (subject to
appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization), resulting in at least $40,000,000 of aggregate gross proceeds to the Company; if such a public offering is consummated before
March 15, 2012, no minimum offering price or aggregate gross proceeds thresholds apply), and (b) the consummation of a Deemed Liquidation Event (as defined in the Company’s Amended and Restated Articles of Incorporation).”

 4. Except as amended as set forth above, the IRA, the Voting Agreement and the ROFR and Co-Sale Agreement shall continue in
full force and effect. 
 5. Miscellaneous. 

(a) Successors and Assigns. This Amendment shall be binding upon and shall inure to the benefit of the parties’
respective successors and assigns. 
 (b) Authority. Each of the signatories hereto certifies that such
party has all necessary authority to execute this Amendment. 
 (c) Counterparts; Facsimile. This
Amendment may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument. Facsimile signatures shall be as effective as original signatures.

 [Signature Page Follows] 

  
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 IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly executed as of
the date first written above. 
  

			
	PROTO LABS, INC.
		
	By:	 	 /s/ Bradley A. Cleveland

		 	Bradley A. Cleveland, President and Chief Executive Officer
	
	        /s/ Lawrence J. Lukis

	       Lawrence J. Lukis, individually
	
	PROTOMOLD INVESTMENT COMPANY, LLC
		
	By:	 	 /s/ Brian K. Smith

		 	Brian K. Smith, Chief Manager
	
	NORTH BRIDGE GROWTH EQUITY I, L.P.
		
	By:	 	North Bridge Growth Management, L.P., its General Partner
	
	By: NBGE GP, LLC, its General Partner
		
	By:	 	 /s/ Douglas Kingsley

		 	Douglas Kingsley, Partner

  
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