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SUBSIDIARY GUARANTOR SUPPLEMENT THIS SUBSIDIARY GUARANTOR SUPPLEMENT (the
“Subsidiary Guarantor Supplement”), dated as of August 22, 2018 is made by each
of REACTION TECHNOLOGY EPI, LLC, a Delaware limited liability company, and
REACTION TECH RE, LLC, a Delaware limited liability company (each, an
“Additional Subsidiary Guarantor”), in favor of the holders from time to time of
the Notes issued pursuant to the Note Agreement described below: PRELIMINARY
STATEMENTS: I. Pursuant to the Note Purchase Agreement dated as of December 8,
2016 (as amended, modified, supplemented or restated from time to time, the
“Note Agreement”), by and among LITTELFUSE, INC., a Delaware corporation
(together with any successor thereto that becomes a party to the Note Agreement
pursuant to Section 10.2, the “Company”) and the Persons listed on the signature
pages thereto (the “Purchasers”), the Company has issued and sold (i)
$25,000,000 aggregate principal amount of its 3.03% Senior Notes, Series A, due
February 15, 2022 (the “Series A Notes”) and (ii) $100,000,000 aggregate
principal amount of its 3.74% Senior Notes, Series B, due February 15, 2027 (the
“Series B Notes” and together with the Series A Notes as amended, restated or
otherwise modified from time to time and including any such notes issued in
substitution therefor, the “Notes” and individually a “Note”). II. The Company
is required pursuant to the Note Agreement to cause each Additional Subsidiary
Guarantor to deliver this Subsidiary Guarantor Supplement in order to cause each
Additional Subsidiary Guarantor to become a Subsidiary Guarantor under the
Subsidiary Guaranty Agreement dated as of February 15, 2017 executed by certain
Subsidiaries of the Company (together with each entity that from time to time
becomes a party thereto by executing a Subsidiary Guarantor Supplement pursuant
to Section 14.1 thereof, collectively, the “Subsidiary Guarantors”) in favor of
each holder from time to time of any of the Notes (as the same may be amended,
restated, supplemented or otherwise modified from time to time, the “Subsidiary
Guaranty Agreement”). III. Each Additional Subsidiary Guarantor has received and
will receive substantial direct and indirect benefits from the Company’s
compliance with the terms and conditions of the Note Agreement and the Notes
issued thereunder. IV. Capitalized terms used and not otherwise defined herein
have the definitions set forth in the Note Agreement. Now therefore, in
consideration of the funds advanced to the Company by the Purchasers under the
Note Agreement and to enable the Company to comply with the terms of the Note
Agreement, each Additional Subsidiary Guarantor hereby covenants, represents and
warrants to the holders as follows:

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The Additional Subsidiary Guarantor hereby becomes a Subsidiary Guarantor (as
defined in the Subsidiary Guaranty Agreement) for all purposes of the Subsidiary
Guaranty Agreement. Without limiting the foregoing, the Additional Subsidiary
Guarantor hereby (a) jointly and severally with the other Subsidiary Guarantors
under the Subsidiary Guaranty Agreement (including the other Additional
Subsidiary Guarantors party to this Subsidiary Guarantor Supplement), guarantees
to the holders from time to time of the Notes the prompt payment in full when
due (whether at stated maturity, by acceleration or otherwise) and the full and
prompt performance and observance of all Guaranteed Obligations (as defined in
Section 1 of the Subsidiary Guaranty Agreement) in the same manner and to the
same extent as is provided in the Subsidiary Guaranty Agreement, (b) accepts and
agrees to perform and observe all of the covenants set forth therein, (c) waives
the rights set forth in Section 3 of the Subsidiary Guaranty Agreement, (d)
agrees to perform and observe the covenants contained in Section 8 of the
Subsidiary Guaranty Agreement, (e) makes the representations and warranties set
forth in Section 9 of the Subsidiary Guaranty Agreement and (f) waives the
rights, submits to jurisdiction, and waives service of process as described in
Section 14.6 of the Subsidiary Guaranty Agreement. Notice of acceptance of this
Subsidiary Guarantor Supplement and of the Subsidiary Guaranty Agreement, as
supplemented hereby, is hereby waived by the Additional Subsidiary Guarantor.
The address for notices and other communications to be delivered to the
Additional Subsidiary Guarantor pursuant to Section 13 of the Subsidiary
Guaranty Agreement is set forth on the signature page below. [REMAINDER OF PAGE
INTENTIONALLY LEFT BLANK] 2 4853-2391-8191.2

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