Masimo Corp (MASI): Pentwater Capital files 13G/A showing exit from common stock

Rhea-AI Filing Summary

Pentwater Capital Management LP and Matthew Halbower filed an amended Schedule 13G indicating that they no longer beneficially own common stock of Masimo Corporation. The filing reports 0 shares beneficially owned and a 0.0% ownership of Masimo’s common stock, with no sole or shared voting or dispositive power.

Key Figures

Beneficial ownership: 0 shares Percent of class owned: 0.0% Par value per share: $0.001 per share +1 more

4 metrics

Beneficial ownership 0 shares Masimo common stock reported as beneficially owned by the reporting persons

Percent of class owned 0.0% Ownership percentage of Masimo common stock reported for the class

Par value per share $0.001 per share Par value of Masimo Corporation common stock

CUSIP 574795100 CUSIP number for Masimo Corporation common stock

Key Terms

beneficially owned, sole voting power, dispositive power, Schedule 13G

4 terms

beneficially owned financial

"Amount beneficially owned: The information required by Item 4(a)..."

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole voting power financial

"Sole Voting Power 0.00 6 | Shared Voting Power 0.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

dispositive power financial

"Sole Dispositive Power 0.00 8 | Shared Dispositive Power 0.00"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

Schedule 13G regulatory

"Ownership of 5 percent or less of a class "

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

FAQ

What does the Schedule 13G/A filing say about Pentwater’s ownership in MASI?

The amended filing reports that Pentwater Capital Management LP and Matthew Halbower now have 0 shares beneficially owned, representing 0.0% of Masimo Corporation’s common stock, and no sole or shared voting or dispositive power.

Who are the reporting persons in this MASI Schedule 13G/A amendment?

The reporting persons are Pentwater Capital Management LP, a Delaware limited partnership investment manager, and Matthew Halbower, a United States citizen and the sole shareholder of MCH PWCM Holdings Inc., the general partner of the investment manager.

What class of securities is covered in Pentwater’s MASI Schedule 13G/A?

The filing covers Masimo Corporation’s common stock, par value $0.001 per share. The CUSIP associated with this class of securities is 574795100, and the amendment reflects updated ownership information for this class.

What is the reported percentage of MASI common stock owned by Pentwater?

Pentwater Capital Management LP and Matthew Halbower report owning 0.0% of Masimo Corporation’s common stock. The amendment also confirms they have no sole or shared voting or dispositive power over any Masimo shares.

Where is the business office of the reporting persons in the MASI Schedule 13G/A?

The business office for both Pentwater Capital Management LP and Matthew Halbower is listed as 1001 10th Avenue South, Suite 216, Naples, FL 34102, which serves as the principal business address in the ownership report.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/14/2026 - 04:29 PM Accepted by SEC EDGAR 08/14/2026 - 04:23 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

MASIMO CORP

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

574795100

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 574795100

1

Names of Reporting Persons

Pentwater Capital Management LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

0.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): 574795100

1

Names of Reporting Persons

Matthew Halbower

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

0.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MASIMO CORP
(b)	Address of issuer's principal executive offices: 52 Discovery, Irvine, California 92618
Item 2.
(a)	Name of person filing: This statement is filed by: (i) Pentwater Capital Management LP (the "Investment Manager"), a Delaware limited partnership, and the investment adviser to certain funds (the "Pentwater Funds"), with respect to the shares of common stock, par value $0.001 per share ("Common Stock"), of Masimo Corporation, a Delaware corporation, that were directly held by the Pentwater Funds; and (ii) Mr. Matthew Halbower ("Mr. Halbower"), the sole shareholder of MCH PWCM Holdings Inc., the general partner of the Investment Manager, with respect to the shares of Common Stock that were directly held by the Pentwater Funds. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons."
(b)	Address or principal business office or, if none, residence: The address of the business office of each of the Reporting Persons is 1001 10th Avenue South, Suite 216, Naples, FL 34102.
(c)	Citizenship: The Investment Manager is a Delaware limited partnership. Mr. Halbower is a citizen of the United States.
(d)	Title of class of securities: Common Stock, par value $0.001 per share
(e)	CUSIP No.: 574795100
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
(b)	Percent of class: 0.0%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Pentwater Capital Management LP

Signature:	/s/ Matthew Halbower
Name/Title:	By: MCH PWCM Holdings Inc., General Partner, By: Matthew Halbower, Chief Executive Officer
Date:	08/14/2026

Matthew Halbower

Signature:	/s/ Matthew Halbower
Name/Title:	Matthew Halbower, individually
Date:	08/14/2026