MASIMO (MASI) CEO Szyman exercises RSUs, withholds shares to cover tax

Rhea-AI Filing Summary

MASIMO CORP CEO Catherine M. Szyman reported routine equity compensation activity. On March 11, she exercised 2,101 restricted stock units into 2,101 shares of common stock at a conversion price of $0.00 per share, reflecting a scheduled vesting event.

To cover related tax obligations, 1,069 of the newly issued shares were withheld by the company at a price of $175.47 per share, leaving a net increase in her direct common stock holdings. After these transactions, she directly holds 7,605 shares of common stock and 6,306 remaining restricted stock units.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Szyman Catherine M.

(Last) (First) (Middle)

C/O MASIMO CORPORATION

52 DISCOVERY

(Street)

IRVINE CA 92618

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
MASIMO CORP [ MASI ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	CEO

3. Date of Earliest Transaction (Month/Day/Year)
03/11/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	03/11/2026		M		2,101(1)	A	$0	8,674	D
Common Stock	03/11/2026		F		1,069(2)	D	$175.47	7,605	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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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)	03/11/2026		M			2,101	(1)	03/11/2035	Common Stock	2,101	$0	6,306	D

Explanation of Responses:

1. As previously reported, the reporting person was granted 8,407 restricted stock units (RSUs) on March 11, 2025 and will vest ratably over four years, 25% of which vested on March 11, 2026.

2. 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 RSUs.

3. Each RSU represents the contingent right to receive one share of common stock of the Issuer upon vesting of the RSU.

Remarks:

	/s/ Micah W. Young, Attorney-In-Fact	03/16/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider transaction did MASIMO CORP (MASI) CEO Catherine M. Szyman report?

Catherine M. Szyman reported exercising 2,101 restricted stock units into 2,101 shares of MASIMO CORP common stock. This was a scheduled vesting event, not an open-market purchase, and reflects routine equity compensation rather than a discretionary trade in the company’s shares.

How many MASIMO (MASI) shares were withheld for taxes in Catherine Szyman’s Form 4?

The filing shows 1,069 MASIMO CORP common shares were withheld to satisfy tax obligations. These shares were valued at $175.47 each and represent payment of taxes on vested restricted stock units, not an open-market sale of existing shareholdings.

How did this Form 4 change Catherine Szyman’s MASIMO (MASI) share ownership?

After the transactions, Catherine Szyman directly holds 7,605 shares of MASIMO CORP common stock. She also retains 6,306 outstanding restricted stock units, which may convert into additional shares in future vesting periods, subject to continued service and applicable award conditions.

Are Catherine Szyman’s MASIMO (MASI) Form 4 transactions considered open-market trades?

No, the reported transactions are not open-market trades. They reflect the exercise of restricted stock units and withholding of shares to pay associated tax liabilities. This type of activity is typical for executive equity compensation programs at public companies like MASIMO CORP.

What is the size of the restricted stock unit award in Catherine Szyman’s MASIMO (MASI) filing?

The filing notes a grant of 8,407 restricted stock units on March 11, 2025. These RSUs vest ratably over four years, with 25% vesting on March 11, 2026, and each unit representing the right to receive one MASIMO CORP common share upon vesting.