Sec Form 4 Filing - Young Micah W @ MASIMO CORP - 2025-03-01

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Young Micah W 2. Issuer Name and Ticker or Trading Symbol MASIMO CORP [ MASI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP & Chief Financial Officer (Last) (First) (Middle) C/O MASIMO CORPORATION, 52 DISCOVERY 3. Date of Earliest Transaction (MM/DD/YY) 03/01/2025 (Street) IRVINE, CA92618 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/01/2025 M 15,000 A $ 0 25,536 D Common Stock 03/01/2025 F 8,100 ( 1 ) D $ 188.77 ( 2 ) 17,436 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Restricted Stock Units ( 3 ) 03/01/2025 M 15,000 ( 4 ) ( 4 ) Common Stock 15,000 $ 0 15,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Young Micah W C/O MASIMO CORPORATION 52 DISCOVERY IRVINE, CA92618 EVP & Chief Financial Officer Signatures /s/ Micah W. Young, Attorney-In-Fact 03/04/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These shares were withheld by the Issuer in order to satisfy certain tax withholding obligations in connection with the issuance of shares upon the vesting of certain performance restricted stock units. ( 2 )For the vesting that occurred on March 1, 2025, the Company calculated the number of vested shares and shares withheld for tax liability based on the Company's closing stock price on the immediately preceding business day. As a result, the Reporting person received 6,900 shares of common stock, as shown in Table I. ( 3 )Each restricted stock unit (RSU) represents the contingent right to receive one share of common stock of the Issuer upon vesting of the RSU. ( 4 )As previously reported, the reporting person was granted 30,000 restricted stock units on March 1, 2024, 50% of which will vest on March 1, 2025 and 50% of which will vest on March 1, 2026. The remaining 15,000 restricted stock units are shown in table II and are scheduled to vest on March 1, 2026.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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