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EXHIBIT 4(c)  

  Letter to Rights Warrant Holders         

August  ,
2000 

[warrant
holder name]

[warrant holder address -1]

[warrant holder address -2] 

Dear
Warrant Holder: 

    Oxboro
Medical, Inc. has commenced an Incentive Warrant Offering to the holders of the Company's common stock purchase warrants issued in connection with the Company's
September 1, 1999 rights offering (the "Right Warrants"). As an incentive to encourage exercise of the Rights Warrants, the Company is offering to each holder of the Rights Warrants a common
stock purchase warrant (the "Incentive Warrants"). In order to receive an Incentive Warrant, you must exercise your Rights Warrant on or before September 30, 2000. There
is no additional cost to you associated with the issuance of the Incentive Warrant. We will issue you an Incentive Warrant permitting you to purchase that number of shares of
common stock equal to that number of shares of common stock you acquired pursuant to your exercise of your Rights Warrant on or before September 30, 2000. The per share exercise price of an
Incentive Warrant is $      . 

    Enclosed
is a Prospectus dated August      , 2000, together with a Warrant Exercise and Ownership Representation Agreement. You are encouraged to carefully review the
Prospectus. The Warrant Exercise and Ownership Representation Agreement included with the prospectus must be completed and returned with the payment required for exercise of
the Rights Warrants on or before September 30, 2000. All appropriate documentation and payments must be received on or before September 30, 2000. Following this period, you may exercise
your Rights Warrants until the expiration date specified on the Rights Warrant, but you will be issued no Incentive Warrants unless the Rights Warrant is exercised on or before September 30,
2000.

    Please
contact Matthew E. Bellin, President, at Oxboro Medical, Inc., 13828 Lincoln Street NE, Ham Lake, Minnesota 55304 if you have questions concerning your rights to receive
Incentive Warrants pursuant to this offering. 

Very
truly yours, 

MATTHEW E. BELLIN
President

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EXHIBIT 4(d)  

  WARRANT AGREEMENT         

    THIS AGREEMENT is made as of the        day of September, 2000, by and between Oxboro Medical, Inc. (the "Company") and the
Wells Fargo Bank Minnesota, National Association, South St. Paul, Minnesota (the "Warrant Agent"). 

  RECITALS         

    The Company proposes to issue Common Stock Purchase Warrants (the "Warrants") evidencing the right to purchase an aggregate of up to 417,794 authorized but
previously unissued shares of Common Stock, $.01 par value per share, of the Company (the "Common Stock"). 

    The
Company desires the Warrant Agent to act on behalf of the Company, and the Warrant Agent desires so to act, in connection with the issuance, registration, transfer, exchange and
exercise of the Warrants. 

    The
Company and the Warrant Agent, each intending to be legally bound, hereby covenant and agree as follows: 

  ARTICLE 1
       APPOINTMENT OF WARRANT AGENT; ISSUANCE,
  FORM AND EXECUTION OF WARRANT CERTIFICATES         

    1.1)  Appointment of Warrant Agent.  The Company hereby appoints the Warrant Agent to act as agent for
the Company, and the Warrant Agent hereby accepts the agency established hereby and agrees to perform its agency duties in accordance with the terms and conditions of this Warrant Agreement. 

    1.2)  Warrant Certificates.  The Company shall execute and deliver to the Warrant Agent certificates that
the Company has authorized to represent the Warrants ("Warrant Certificates"). The Warrant Certificates shall be substantially as set forth in Exhibit A hereto and may have such legends,
summaries or endorsements printed, lithographed or engraved thereon as the Company may deem appropriate and as are not inconsistent with the provisions of this Warrant Agreement, or as may be required
to comply with any law or with any rule or regulation of any stock exchange on which the Warrants may be listed, or to conform to usage. The Warrant Certificates shall be dated the date of their
issuance. 

    1.3)  Execution of Warrant Certificates.  The Warrant Certificates shall be executed on behalf of the
Company by a duly authorized officer of the Company, either manually or by facsimile signature printed thereon. The Warrant Certificates shall be manually countersigned by the Warrant Agent and shall
not be valid for any purpose unless so countersigned. Any Warrant Certificate may be signed on behalf of the Company by the person who at the actual date of the signing of such Warrant Certificate
shall have been the proper officer of the Company, although at the date of issuance of such Warrant Certificate any such person shall not be such officer of the Company. 

  ARTICLE 2
       EXERCISE OF WARRANTS         

    2.1)  Exercise.  Any or all of the Warrants represented by each Warrant Certificate may be exercised by
the holder thereof on any business day in the period beginning at 10:00 a.m. Minneapolis time on day after issuance and ending at 5:00 p.m. Minneapolis time on September 29, 2003,
the Warrant Expiration Date, by surrender of the Warrant Certificate with the Purchase Form, which is printed on the reverse thereof (or a reasonable facsimile thereof), duly executed by such holder,
to the Warrant Agent at its principal office in South St. Paul, Minnesota, accompanied by payment, in cash or by certified or official bank check payable to the order of the Company, in an amount
equal to the 

product of the number of shares of Common Stock to be issued upon exercise of the Warrant represented by such Warrant Certificate, as adjusted pursuant to the provisions of Article 3 hereof,
multiplied by the exercise price then in effect (such price as so adjusted from time to time being herein called the "Exercise Price"), and such holder shall be entitled to receive such number of
fully paid and nonassessable shares of Common Stock, as so adjusted, at the time of such exercise. 

    2.2)  Time of Exercise.  Each exercise of Warrants shall be deemed to have been effective immediately
prior to the close of business on the business day on which the Warrant Certificate relating to such Warrants shall have been surrendered to the Warrant Agent as provided in Article 2.1, and at
such time the person or persons in whose name or names any certificate or certificates for shares of Common Stock shall be issuable upon such exercise as provided in Article 2.3, shall be
deemed to have become the holder or holders of record thereof. 

    2.3)  Issuance of Shares of Common Stock; No Fractional Shares.  As soon as practicable after the
exercise of any Warrant, and in any event within 10 days thereafter, the Company at its expense (including the payment by it of any applicable issue taxes) will cause to be issued in the name
of and delivered to the holder thereof or as such holder (upon payment by such holder of any applicable transfer taxes) may direct, 

	(a)
	a
certificate or certificates for the number of fully paid and nonassessable shares of Common Stock to which such holder shall be entitled upon such exercise plus, in lieu of any
fractional share to which such holder would otherwise be entitled, an amount in cash equal to such fraction multiplied by the Market Price of the Company's Common Stock as determined in
Section 3.2 of this Agreement.

	(b)
	in
case such exercise includes only part of the Warrants represented by any Warrant Certificate, a new Warrant Certificate or Warrant Certificates of like tenor, calling in the
aggregate on the face or faces thereof for the number of shares of Common Stock equal (without giving effect to any adjustment therein) to the number of such shares called for on the face of such
Warrant Certificate minus the number of such shares designated by the holder for such exercise as provided in Article 2.1. 

    2.4)  Assigned Warrant Certificates.  Warrants, represented by a properly assigned Warrant Certificate,
may be exercised by a new holder without first having a new Warrant Certificate issued. 

  ARTICLE 3
       WARRANT PRICE; ADJUSTMENT OF WARRANT PRICE AND
  NUMBER OF WARRANT SHARES         

    3.1)  Establishment of Exercise Price.  Subject to adjustment as hereinafter provided, the Exercise Price
per share of Common Stock shall be $      . 

    3.2)  Adjustments.  The per share Exercise Price and the number of Shares deliverable hereunder shall be
adjusted as hereinafter set forth. If after the date hereof, the Company shall: 

	(1)
	take
a record of the holders of its Common Stock for the purposes of entitling them to receive a dividend payable in, or other distribution of, Common Stock; or

	(2)
	subdivide
its outstanding shares of Common Stock into a larger number of shares of Common Stock; or

	(3)
	combine
its outstanding shares of Common Stock into a smaller number of shares of Common Stock; or

	(4)
	issue
by reclassification of its shares of Common Stock any other shares of Common Stock; 

2

Then
the number of shares of Common Stock purchasable upon exercise of each Warrant immediately prior thereto shall be adjusted so that the holder of each Warrant shall be entitled to receive the kind
and number of shares of Common Stock or other securities of the Company which he or it would have owned or have been entitled to receive after the happening of any of the events described above, had
such Warrant been exercised immediately prior to the happening of such event or record date with respect thereto. An adjustment made pursuant to this paragraph (a) shall become effective
immediately after the effective date of such event, retroactive to the record date, if any, for such event. 

    3.3)  Consolidation, Merger or Combination.  In the case of any consolidation or merger of the Company
with another corporation, or the sale of all or substantially all of its assets to another person, or any
reorganization or reclassification of the capital stock of the Company (except a split-up or combination provision for which provision is made in Article 3.2), then: 

	(a)
	As
a condition of such consolidation, merger, sale, reorganization or reclassification, lawful and adequate provision shall be made whereby the holder shall thereafter have the
right to receive upon the basis and upon the terms and conditions specified herein and in lieu of the shares of the Common Stock immediately theretofore subject to acquisition hereunder, such shares
of stock, securities or assets as may (by virtue of such consolidation, merger, sale, reorganization or reclassification) be issued or payable with respect to or in exchange for a number of
outstanding shares of such common stock equal to the number of shares of such Common Stock immediately theretofore so subject to acquisition hereunder had such consolidation, merger, sale,
reorganization or reclassification not taken place, and in any such case appropriate provisions shall be made with respect to the rights and interests of the holder to the end that the provisions
hereof (including, without limitation, provisions for adjustments of the Exercise Price) shall thereafter be applicable as nearly as may be, in relation to any shares of stock, securities or assets
thereafter deliverable upon the exercise of the conversion option. The Company shall not effect any such consolidation, merger or sale, unless prior to or simultaneously with the consummation thereof,
the successor person or persons purchasing such assets or succeeding or resulting from such consolidation, merger, reorganization or reclassification shall assume by written instrument executed and
mailed or delivered to the holder, the obligation to deliver to such holder such shares of stock, securities or assets as, in accordance with the foregoing provisions, the holder may be entitled to
receive.

	(b)
	In
the event that the Company shall make any distribution of its assets upon or with respect to its Common Stock, as a liquidating or partial liquidation dividend, or other than as
a dividend payable out of earnings or any surplus legally available for dividends under the laws of the State of Minnesota, the holder shall, upon the exercise of his right to convert after the record
date for such distribution or, in the absence of a record date, after the date of such distribution, receive in addition to the shares subscribed for, the amount of such assets (or, at the option of
the Company, a sum equal to the value thereof at the time of distribution as determined in good faith by the Board of Directors in its sole discretion) which would have been distributed to the holder
if he or it had exercised his or its Warrants immediately prior to the record date for such distribution or, in the absence of a record date, immediately prior to the date of such distribution). 

    3.4)  Fractional Shares.  Fractional shares shall not be issued upon the exercise of any Warrant but in
any case where the holder would, except for the provisions of this Article, be entitled under the terms hereof to receive a fractional share, the Company shall, upon the exercise of any Warrant for
the largest number of whole shares then called for, pay a sum in cash equal to the sum of (a) the excess, if any, of the Market Price of such fractional share over the proportional part of the
per share Exercise Price represented by such fractional share plus (b) the proportional part of the per share Exercise Price represented by such
fractional share. 

3

    3.5)  Reservation and Listing of Common Stock.  The Company will at all times reserve solely for issuance
and delivery upon the exercise of the Warrants, all shares of Common Stock from time to time issuable upon such exercise. All such shares shall be duly authorized and, when issued upon such exercise,
shall be validly issued, fully paid and nonassessable with no liability on the part of the holder thereof. The Company at its expense will list on each national securities exchange on which any Common
Stock may at any time be listed, subject to official notice of issuance, and will maintain such listing of, the shares of Common Stock from time to time issuable upon the exercise of the Warrants. 

    3.6)  Registration of Common Stock.  The Company will at all times there are Warrants outstanding use its
best efforts to (i) maintain an effective registration statement under the Securities Act of 1933, as amended (the "Act"), covering Common Stock issuable in respect of the Warrants, and from
time to time shall amend or supplement the prospectus contained in such registration statement to the extent necessary in order to comply with applicable law and (ii) maintain qualifications in
those jurisdictions in which the Rights were initially qualified to permit exercise of the Warrants and the issuance of the Common Stock pursuant to such exercise. 

  ARTICLE 4
       CERTAIN OTHER PROVISIONS RELATING TO RIGHTS
  OF HOLDERS OF WARRANT CERTIFICATES         

    4.1)  No Rights of Shareholders.  The warrant Certificates shall be issued in registered form only. No
Warrant Certificate shall entitle the holder thereof to any of the rights of a holder of shares of Common Stock of the Company, including, without limitation, the right to vote, to receive dividends
and other distributions, or to receive any notice of, or to attend, meetings of holders of Common Stock or any other proceedings of the Company. 

    4.2)  Loss, Theft, Etc. of Warrant Certificates.  Upon receipt by the Warrant Agent of evidence
reasonably satisfactory to the Warrant Agent of the loss, theft, destruction or mutilation of any Warrant Certificate and, in the case of any such loss, theft, or destruction, upon delivery to the
Warrant Agent of an indemnity bond in form and amount, and issued by a bonding company, reasonably satisfactory to the Company (or, in the case of any Warrant Certificate held by an institutional
investor, an indemnity
agreement reasonably satisfactory to the Company), or, in the case of any such mutilation, upon surrender to and cancellation by the Warrant Agent of such Warrant Certificate, the Company at its
expense will execute and cause the Warrant Agent to countersign and deliver, in lieu thereof, a new Warrant Certificate of like tenor. 

    4.3)  No Adequate Remedy at Law.  The Company stipulates that the remedies at law of the holders of the
Warrants in the event of any default or threatened default by the Company in the performance of or compliance with any of the terms of this Warrant Agreement and the Warrant Certificates are not and
will not be adequate, and that such terms may be specifically enforced by a decree for the specific performance of any agreement contained in this Warrant Agreement and the Warrant Certificates or by
an injunction against a violation of any of the terms of this Warrant Agreement and the Warrant Certificates or otherwise. 

    4.4)  Transfer Agent; Cancellation of Warrant Certificates; Unexercised Warrants.  Wells Fargo Bank
Minnesota, National Association (and any successor), as the Company's transfer agent (the "Transfer Agent"), is hereby irrevocably authorized and directed at all times to reserve such number of
authorized and unissued shares of Common Stock as shall be sufficient to permit the exercise in full of all Warrants from time to time outstanding. The Company will keep a copy of this Agreement on
file with the Transfer Agent. The Warrant Agent, and any successor thereto, is hereby irrevocably authorized to requisition from time to time from the Transfer Agent certificates for shares of Common
Stock required for exercises of Warrants. The Company will supply the Transfer Agent with duly executed certificates for shares of Common Stock for such purpose and will make available any cash
required in settlement of fractional share interests. All Warrant Certificates surrendered upon the 

4

exercise or redemption of Warrants shall be cancelled by the Warrant Agent and shall thereafter be delivered to the Company; such cancelled Warrant Certificates, with the Purchase Form on the reverse
thereof duly filled in and signed, shall constitute conclusive evidence as between the parties hereto of the numbers of shares of Common Stock which shall have been issued upon exercises of Warrants.
Promptly after the Expiration Date of the Warrants, the Warrant Agent shall certify to the Company the aggregate number of Warrants then outstanding and unexercised. No shares of Common Stock shall be
subject to reservation with respect to Warrants not exercised prior to 5:00 p.m. Minneapolis time on the Expiration Date. 

  ARTICLE 5
       TRANSFER AND EXCHANGE OF WARRANT CERTIFICATES         

    5.1)  Warrant Register; Transfer or Exchange of Warrant Certificates.  The Warrant Agent shall cause to
be kept at the principal office of the Warrant Agent a register (the "Warrant Register") in which, subject to such reasonable regulations as the Company may prescribe, provisions shall be made for the
registration of transfers and exchanges of Warrant Certificates. Upon surrender for transfer or exchange of any Warrant Certificates, properly endorsed, to the Warrant Agent, the Warrant Agent at the
Company's expense will issue and deliver to or upon the order of the holder thereof a new Warrant Certificate or Warrant Certificates of like tenor, in the name of such holder or as such holder (upon
payment by such holder of any applicable transfer taxes) may direct, calling in the aggregate on the face or faces thereof for the number of shares of Common Stock called for on the face of the
Warrant Certificate so surrendered. Any warrant Certificate surrendered for transfer or exchange shall be cancelled by the Warrant Agent and shall thereafter be delivered to the Company. 

    5.2)  Identity of Warrant Holders.  Until a Warrant Certificate is transferred in the Warrant Register,
the Company and the Warrant Agent may treat the person in whose name the Warrant Certificate is registered as the absolute owner thereof and of the Warrants represented thereby for all purposes,
notwithstanding any notice to the Contrary, except that, if and when any Warrant Certificate is properly assigned in blank, the Company and the Warrant Agent may (but shall not be obligated to) treat
the bearer thereof as the absolute owner of the Warrant Certificate and of the Warrants represented thereby for all purposes, notwithstanding any notice to the contrary. 

  ARTICLE 6
       CONCERNING THE WARRANT AGENT         

    6.1)  Taxes.  The Company will from time to time promptly pay to the Warrant Agent, or make provision
satisfactory to the Warrant Agent for the payment of, all taxes and charges that may be imposed by the United States or any State upon the Company or the Warrant Agent upon the transfer or delivery of
shares of Common Stock upon the exercise of Warrants, but the Company shall not be obligated to pay any tax imposed in connection with any transfer involved in the delivery of a certificate for shares
of Common Stock in any name other than that of the registered holder of the Warrant Certificate surrendered in connection with the purchase thereof. 

    6.2)  Replacement of Warrant Agent in Certain Circumstances.  

	(a)
	The
Warrant Agent may resign its duties and be discharged from all further duties and liabilities hereunder after giving 30 days' notice in writing to the Company, except
that such shorter notice may be given as the Company shall, in writing, accept as sufficient. The Company may discharge the Warrant Agent at any time with or without reason, effective upon
30 days' written notice to the Warrant Agent or such shorter period as the Warrant Agent shall, in writing, accept as sufficient. If the office of Warrant Agent becomes vacant by resignation,
discharge, incapacity to act or otherwise, the Company shall appoint in writing a new Warrant Agent, the principal office of which shall be in Minnesota. If the Company shall fail to make such
appointment within a period of 

5

30 days
after it has been notified in writing of such resignation or incapacity by the resigning or incapacitated Warrant Agent or by the holder of a Warrant Certificate, then the holder of any
Warrant Certificate may apply to any court of competent jurisdiction for the appointment of a new Warrant Agent. Any new Warrant Agent, whether appointed by the Company or by such a court, shall be a
corporation organized and doing business under the laws of the United States or of the State of Minnesota, of good standing, and having its principal office in Minnesota, which is authorized under
such laws to exercise corporate trust cowers and is subject to supervision or examination by a Federal or State authority. Any new Warrant Agent appointed hereunder shall execute, acknowledge and
deliver to the Company an instrument accepting such appointment hereunder and thereupon such new Warrant Agent without any further act or deed shall become vested with all the rights, powers, duties
and responsibilities of the Warrant Agent hereunder with like effect as if it had been named as the Warrant Agent; but if for any reason it becomes necessary or expedient to have the former Warrant
Agent execute and deliver any further assurance, conveyance, act or deed, the same shall be done at the expense of the Company and shall be legally and validly executed and delivered by the former
Warrant Agent. Not later than the effective date of any such appointment the Company shall file notice thereof with the former Warrant Agent. The Company shall promptly give notice of any such
appointment to the holders of the Warrant Certificates by mail to their addresses as shown in the Warrant Register. Failure to file or give such notice, or any defect therein, shall not affect the
legality or validity of the appointment of the successor Warrant Agent. 

	(b)
	Any
company into which the Warrant Agent or any new Warrant Agent may be merged or converted or with which it may be consolidated or any company resulting from any merger,
conversion or consolidation to which the Warrant Agent or any new Warrant Agent shall be a party shall be the successor Warrant Agent under this Warrant Agreement without any further act, provided
that if such company would not be eligible for appointment as a successor Warrant Agent under the provisions of paragraph (a) of this Article 6.2 the Company shall forthwith appoint a
new Warrant Agent in accordance with such provisions. Any such successor Warrant Agent may adopt the prior
countersignature of any predecessor Warrant Agent and deliver Warrant Certificates countersigned and not delivered by such predecessor Warrant Agent or may countersign Warrant Certificates either in
the name of any predecessor Warrant Agent or the name of the successor Warrant Agent. 

    6.3)  Remuneration of Warrant Agent.  The Company will pay the Warrant Agent reasonable remuneration for
its services as Warrant Agent hereunder and will reimburse the Warrant Agent upon demand for all expenditures that the Warrant Agent may reasonably incur in the execution of its duties hereunder. 

    6.4)  Further assurances.  The Company will perform, exercise, acknowledge and deliver or cause to be
performed, executed, acknowledged and delivered all such further and other acts, instruments and assurances as may reasonably be required by the Warrant Agent for the carrying out or performing by the
Warrant Agent of the provisions of this Warrant Agreement. 

    6.5)  Limitations on liabilities of the Warrant Agent.  

	(a)
	The
Warrant Agent may consult with legal counsel (who may be legal counsel for the Company), and the opinion of such counsel shall be full and complete authorization and protection
to the Warrant Agent as to any action taken or omitted by it in good faith and in accordance with such opinion.

	(b)
	Whenever
in the performance of its duties under this Warrant Agreement the Warrant Agent shall deem it necessary or desirable that any matter be proved or established, or 

6

that
any instructions with, respect to the performance of its duties hereunder be given, by the Company prior to taking or suffering any action hereunder, such matter (unless other evidence in respect
thereof be herein specifically prescribed) may be deemed to be conclusively proved and established, or such instructions may be given, by a certificate or instrument signed by an officer of the
company and delivered to the Warrant Agent; and such certificate or instrument shall be full authorization to the Warrant Agent for any action taken or suffered in good faith by it under the
provisions of this Warrant Agreement in reliance upon such certificate or instrument; but in its discretion the Warrant Agent may in lieu thereof accept other evidence of such matter or may require
such further or additional evidence as it may deem reasonable. 

	(c)
	The
Warrant Agent shall be liable hereunder only for its own negligence or willful misconduct. The Warrant Agent shall act hereunder solely as agent, and its duties shall be
determined solely by the provisions hereof. The Company agrees to indemnify the Warrant Agent and save it harmless against any and all liabilities, including judgments, costs and counsel fees, for
anything done or omitted by the Warrant Agent in the execution of this Warrant Agreement except as a result of the Warrant Agent's negligence or willful misconduct.

	(d)
	The
Warrant Agent shall not be liable for or by reason of any of the statements of fact of recitals contained in this Warrant Agreement or in the Warrant Certificates (except its
countersignature hereof) or be required to verify the same, but all such statements and recitals are and shall be deemed to have been made by the Company only.

	(e)
	The
Warrant Agent shall not be under any responsibility in respect of the validity of this Warrant Agreement or the execution and delivery hereof or in respect of the validity or
execution of any Warrant Certificate (except its countersignature thereof); nor shall it be responsible for any breach by the Company of any covenant or condition contained in this Warrant Agreement
or in any Warrant Certificate; nor shall it be responsible for the making of any adjustment in the Exercise Price, or number of shares issuable upon exercise of the Warrant Certificates or responsible
for the manner, method or amount of any such adjustment or the facts that would require any such adjustment; nor shall it by any act hereunder be deemed to make any representation or warrant as to the
authorization or reservation of any shares of Common Stock to be issued pursuant to this Warrant Agreement or any Warrant Certificate or as to whether any shares of Common Stock or other securities
are or will be validly authorized and issued and fully paid and nonassessable. 

    6.6)  Amendment and modification.  The Warrant Agent may, without the consent or concurrence of the
holders of the Warrant Certificates, by supplemental agreement or otherwise, join with the Company in making any changes or corrections in this Warrant Agreement that they shall have been advised by
counsel (i) are required to cure any ambiguity or to correct any defective or inconsistent provision or clerical omission or mistake or manifest error herein contained, (ii) add to the
obligations thereafter to be observed by it, or surrender any right or power reserved to or conferred upon the Company in this Warrant Agreement, or (iii) do not or will not adversely affect,
alter or change the rights, privileges or immunities of the holders of Warrant Certificates; provided, however, that any term of this Warrant Agreement or any Warrant Certificate may be changed,
waived, discharged or terminated by an instrument in writing signed by each party against which enforcement of such change, waiver, discharge or termination is sought, or by which the same is to be
performed or observed. 

7

  ARTICLE 7
       OTHER MATTERS         

    7.1)  Successors and assigns.  All the covenants and provisions of this Warrant Agreement by or for the
benefit of the Company or the Warrant Agent shall bind and inure to the benefit of their respective successors and assigns. 

    7.2)  Notices.  Any notice or demand authorized by this Warrant Agreement to be given or made by the
Warrant Agent or by the holder of any Warrant Certificate to or on the Company shall be sufficiently given or made if sent by first-class or registered mail, postage prepaid, addressed (until another
address is filed in writing by the Company with the Warrant Agent) as follows: 

Oxboro
Medical, Inc.

13828 Lincoln Street N.E.

Ham Lake, Minnesota 55304

Attention: Matthew E. Bellin, President 

Any
notice or demand authorized by this Warrant Agreement to be given or made by the holder of any Warrant Certificate or by the Company to in the Warrant Agent shall be sufficiently given or made if
sent by first-class or registered mail, postage prepaid, addressed (until another address is filed in writing by the Warrant Agent with the Company) as follows: 

Wells
Fargo Bank Minnesota, National Association

161 North Concord Exchange

South St. Paul, Minnesota 55705 

    7.3)  Governing law.  This Warrant Agreement and the Warrant Certificates are being delivered in the
State of Minnesota and shall be construed and enforced in accordance with and governed by the law of such State. 

    7.4)  No Benefits Conferred.  Nothing in this Warrant Agreement expressed and nothing that may be implied
from any of the provisions hereof is intended, or shall be construed, to confer upon, or give to, any person or corporation other than the Company, the Warrant Agent, and the holders of the Warrant
Certificates, any right, remedy or claim under or by reason of this Agreement or of any covenant, condition, stipulation, promise or agreement herein; and all covenants, conditions, stipulations,
promises and agreements in this Warrant Agreement contained shall be for the sole and exclusive benefit of the Company, the Warrant Agent, their respective successors, and the holders of the warrant
Certificates. 

    7.5)  Headings.  The descriptive headings used in this Warrant Agreement are inserted for convenience
only and shall not control or affect the meaning or construction of any of the provisions hereof. 

    IN
WITNESS WHEREOF, this Warrant Agreement has been duly executed by the parties hereto as of the day and year first above written. 

OXBORO MEDICAL, INC. 

/s/ MATTHEW E. BELLIN

Matthew E. Bellin, President

WELLS FARGO BANK MINNESOTA, N.A.

By
/s/ SUZANNE M. SWITS

8

QuickLinks

WARRANT AGREEMENT

RECITALS

ARTICLE 1 APPOINTMENT OF WARRANT AGENT; ISSUANCE, FORM AND EXECUTION OF WARRANT CERTIFICATES

ARTICLE 2 EXERCISE OF WARRANTS

ARTICLE 3 WARRANT PRICE; ADJUSTMENT OF WARRANT PRICE AND NUMBER OF WARRANT SHARES

ARTICLE 4 CERTAIN OTHER PROVISIONS RELATING TO RIGHTS OF HOLDERS OF WARRANT CERTIFICATES

ARTICLE 5 TRANSFER AND EXCHANGE OF WARRANT CERTIFICATES

ARTICLE 6 CONCERNING THE WARRANT AGENT

ARTICLE 7 OTHER MATTERS

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