Frontier Capital Reports 3.93% Stake in Ultra Clean

Ultra Clean Holdings, Inc. ownership filing: Frontier Capital Management Co., LLC reports beneficial ownership of 1,787,451 shares of common stock (3.93%) as of 03/31/2026.

Rhea-AI Filing Summary

Ultra Clean Holdings, Inc. ownership filing: Frontier Capital Management Co., LLC reports beneficial ownership of 1,787,451 shares of common stock (3.93%) as of 03/31/2026. The filing shows Frontier has sole voting power over 1,002,952 shares and sole dispositive power over 1,787,451 shares.

Key Figures

Beneficial ownership: 1,787,451 shares Percent of class: 3.93% Sole voting power: 1,002,952 shares +1 more

4 metrics

Beneficial ownership 1,787,451 shares as of 03/31/2026

Percent of class 3.93% percent of common stock

Sole voting power 1,002,952 shares shares with sole voting power

Sole dispositive power 1,787,451 shares shares with sole dispositive power

Key Terms

Schedule 13G/A, beneficially owned, sole dispositive power

3 terms

Schedule 13G/A regulatory

"Item 1. (a) Name of issuer: Ultra Clean Holdings, Inc."

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

beneficially owned financial

"Item 4. (a) Amount beneficially owned: 1,787,451"

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 dispositive power regulatory

"Item 4. (c)(iii) Sole power to dispose or to direct the disposition of: 1,787,451"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake does Frontier Capital report in Ultra Clean Holdings (UCTT)?

Frontier Capital reports beneficial ownership of 1,787,451 shares, representing 3.93% of the class. The Schedule 13G/A lists this amount and the 03/31/2026 time anchor in the filing's ownership table.

How much voting control does Frontier Capital have in UCTT?

The filing shows Frontier has sole voting power over 1,002,952 shares. It lists shared voting power as 0, indicating the reported voting authority is exclusively sole power.

Does Frontier have disposal authority over the UCTT shares it reports?

Yes; the Schedule 13G/A reports Frontier's sole dispositive power as 1,787,451 shares with shared dispositive power 0, indicating sole authority to direct disposition of those shares.

When was the Schedule 13G/A filed and what dates are shown for ownership?

The filing is signed on 05/15/2026 and the ownership table uses an as of 03/31/2026 anchor for the reported share counts. Those two dates appear in the filing text and signature block.

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

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Accepted by SEC EDGAR 05/15/2026 - 08:58 AM EDT 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)

Ultra Clean Holdings, Inc.

(Name of Issuer)

Common stock, par value $0.001 per share

(Title of Class of Securities)

90385V107

(CUSIP Number)

03/31/2026

(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): 90385V107

1

Names of Reporting Persons

FRONTIER CAPITAL MANAGEMENT CO.,LLC

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 1,002,952.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,787,451.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,787,451.00

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)

3.93 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Ultra Clean Holdings, Inc.
(b)	Address of issuer's principal executive offices: 26462 Corporate Avenue Hayward, CA 94545
Item 2.
(a)	Name of person filing: FRONTIER CAPITAL MANAGEMENT CO., LLC
(b)	Address or principal business office or, if none, residence: 99 Summer Street Boston, MA 02110
(c)	Citizenship: Delaware
(d)	Title of class of securities: Common stock, par value $0.001 per share
(e)	CUSIP No.: 90385V107
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: 1,787,451
(b)	Percent of class: 3.93%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 1,002,952
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 1,787,451
	(iv) Shared power to dispose or to direct the disposition of: 0
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.

FRONTIER CAPITAL MANAGEMENT CO.,LLC

Signature:	Robert E. Phay
Name/Title:	Robert E. Phay, Chief Compliance Officer & General Counsel
Date:	05/15/2026