Institutional Ownership Update — Boston Partners Holds 6.26% of MasterBrand (MBC)

Rhea-AI Filing Summary

Boston Partners filed a Schedule 13G/A disclosing beneficial ownership of 7,931,062 shares of MasterBrand, Inc. common stock, representing 6.26% of the class as of 6/30/2025. The filing shows sole voting power over 7,362,454 shares and sole dispositive power over 7,931,062 shares; shared voting and dispositive powers are reported as 0. The shares are held in discretionary client accounts and, by rule, Boston Partners may be deemed a beneficial owner of the reported shares.

The statement includes a certification that the holdings were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control. No group affiliation, subsidiary acquisition, or dissolution of a group is reported. The filing is signed by Akiko Lindholm, Senior Compliance Officer, dated 08/08/2025.

Positive

• Institutional stake disclosed: Boston Partners reports ownership of 7,931,062 shares, equal to 6.26% of MasterBrand's common stock.
• Sole dispositive authority: The filer reports sole voting power for 7,362,454 shares and sole dispositive power for 7,931,062 shares, indicating control over voting and sale decisions for the position.

Negative

• None.

Insights

Financial Analyst

TL;DR Boston Partners reports a material institutional stake of 6.26% (7.93M shares), with sole dispositive control.

Boston Partners' Schedule 13G/A documents a significant passive institutional holding in MasterBrand, Inc. The reported 7,931,062 shares equal 6.26% of the class as of 6/30/2025, which is above the common 5% disclosure threshold and therefore material to holders. The filing shows concentrated sole voting and sole dispositive powers, meaning Boston Partners controls voting direction and disposition decisions for the majority of its position. The filer also certified the position is held in the ordinary course of business and not for control purposes.

Corporate Governance Expert

TL;DR Institutional ownership above 5% is material; Boston Partners declares passive intent and sole control over voting and disposition.

The Schedule 13G/A indicates Boston Partners is a Delaware- organized investment adviser reporting beneficial ownership but asserting that the shares are held in the ordinary course and not to influence control. From a governance perspective, the combination of sole voting power of 7,362,454 and sole dispositive power of 7,931,062 is noteworthy because it centralizes decision authority within the adviser’s discretionary accounts. The filing records no group members or subsidiary acquirers and no other conditions that would suggest an activist or control-seeking stance.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

MASTERBRAND INC

(Name of Issuer)

Common Stock

(Title of Class of Securities)

57638P104

(CUSIP Number)

06/30/2025

(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)

SCHEDULE 13G

CUSIP No. 57638P104

1

Names of Reporting Persons

Boston Partners

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 7,362,454.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 7,931,062.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

7,931,062.00

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)

6.26 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MASTERBRAND INC
(b)	Address of issuer's principal executive offices: 3300 ENTERPRISE PARKWAY, SUITE 300, BEACHWOOD, OHIO 44122
Item 2.
(a)	Name of person filing: Boston Partners
(b)	Address or principal business office or, if none, residence: ONE BEACON STREET 30TH FLOOR BOSTON, Massachusetts 02108
(c)	Citizenship: Boston Partners - DELAWARE
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 57638P104
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: 7,931,062
(b)	Percent of class: 6.26 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Boston Partners - 7,362,454
	(ii) Shared power to vote or to direct the vote: Boston Partners - 0
	(iii) Sole power to dispose or to direct the disposition of: Boston Partners - 7,931,062
	(iv) Shared power to dispose or to direct the disposition of: Boston Partners - 0
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. This Schedule is being filed with respect to 7,931,062.00 shares of Master Brand, Inc. (the Common Stock) held by Boston Partners on 6/30/2025 for the discretionary account of certain clients. By reason of rule 13d-3 under the act Boston Partners may be deemed to be a beneficial owner of such Common Stock. To the knowledge of Boston Partners no person has the right to receive or the power to direct the receipt of dividends from or the proceeds from the sale of such Common Stock which represents more than 5% of the outstanding shares of the Common Stock referred to in item 4(b) hereof.
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.

Boston Partners

Signature:	/s/Akiko Lindholm
Name/Title:	Senior Compliance Officer
Date:	08/08/2025

FAQ

How many MasterBrand (MBC) shares does Boston Partners report owning?

7,931,062 shares, representing 6.26% of the outstanding common stock as of 6/30/2025.

What voting and disposition powers does Boston Partners have over MBC shares?

Sole voting power over 7,362,454 shares and sole dispositive power over 7,931,062 shares; shared powers are reported as 0.

Was the position reported as intended to influence control of MasterBrand (MBC)?

The filing includes a certification that the securities are held in the ordinary course of business and not for the purpose of changing or influencing control, per Item 10.

When is the event date and when was the filing signed?

Event date: 6/30/2025. Signature date: 08/08/2025, signed by Akiko Lindholm, Senior Compliance Officer.

What addresses are listed for MasterBrand and Boston Partners in the filing?

MasterBrand principal office: 3300 Enterprise Parkway, Suite 300, Beachwood, Ohio 44122. Boston Partners: One Beacon Street, 30th Floor, Boston, Massachusetts 02108.