FMR LLC discloses 5.0% MEC stake in Mayville Engineering CO INC (MEC)

Rhea-AI Filing Summary

FMR LLC, a Delaware entity, reports beneficial ownership of 1,280,170.12 shares of MAYVILLE ENGINEERING CO INC common stock, representing 5.0% of the class. FMR LLC has sole power to dispose of these shares and sole voting power over 1,278,023 shares.

Abigail P. Johnson, a U.S. person, reports sole dispositive power over the same 1,280,170.12 shares but no voting power. One or more other persons have rights to receive dividends or sale proceeds from these shares, but no such person holds more than five percent of the outstanding common stock.

Key Figures

Shares beneficially owned: 1,280,170.12 shares Percent of class: 5.0 % Sole voting power: 1,278,023.00 shares +2 more

5 metrics

Shares beneficially owned 1,280,170.12 shares Common stock of MAYVILLE ENGINEERING CO INC reported by FMR LLC

Percent of class 5.0 % Portion of MAYVILLE ENGINEERING CO INC common stock class beneficially owned

Sole voting power 1,278,023.00 shares Shares of MAYVILLE ENGINEERING CO INC over which FMR LLC has sole voting power

Sole dispositive power 1,280,170.12 shares Shares of MAYVILLE ENGINEERING CO INC over which FMR LLC and Abigail P. Johnson have sole dispositive power

Filing date 08/05/2026 Date of signatures by authorized representative for FMR LLC and Abigail P. Johnson

Key Terms

beneficially owned, Sole Voting Power, Sole Dispositive Power, Schedule 13G, +1 more

5 terms

beneficially owned financial

"Ownership (a) | Amount beneficially owned: 1280170.12"

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

"5 | Sole Voting Power 1,278,023.00 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.

Sole Dispositive Power financial

"7 | Sole Dispositive Power 1,280,170.12 8 | Shared Dispositive Power 0.00"

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.

Schedule 13G regulatory

"Please see Exhibit 99 for 13d-1(k) (1) agreement."

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.

parent holding company financial

"If a parent holding company has filed this schedule, pursuant to (ii)(G)"

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

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Available on EDGAR 08/06/2026 - 10:34 AM Accepted by SEC EDGAR 08/06/2026 - 10:33 AM Learn about SEC filing dates

FAQ

What percentage of MAYVILLE ENGINEERING (MEC) common stock does FMR LLC report owning?

FMR LLC reports beneficial ownership of 5.0% of MAYVILLE ENGINEERING CO INC common stock, representing 1,280,170.12 shares with sole dispositive power and voting power over 1,278,023 of those shares.

How many MAYVILLE ENGINEERING (MEC) shares does FMR LLC have voting power over?

FMR LLC has sole voting power over 1,278,023 shares of MAYVILLE ENGINEERING CO INC common stock and no shared voting power, while retaining sole dispositive power over 1,280,170.12 shares.

What is Abigail P. Johnson’s reported interest in MAYVILLE ENGINEERING (MEC)?

Abigail P. Johnson reports sole dispositive power over 1,280,170.12 shares of MAYVILLE ENGINEERING CO INC common stock, representing 5.0% of the class, with no reported sole or shared voting power over these shares.

Do other investors share in the economic interest of FMR LLC’s MEC holdings?

One or more other persons have the right to receive dividends or sale proceeds from the COMMON STOCK of MAYVILLE ENGINEERING CO INC, but no single person’s interest exceeds five percent of the total outstanding common stock.

What type of filing covers FMR LLC’s 5% stake in MAYVILLE ENGINEERING (MEC)?

The ownership of 5.0% of MAYVILLE ENGINEERING CO INC common stock by FMR LLC is reported on a Schedule 13G, a beneficial ownership report used for certain passive or qualified institutional investors.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

MAYVILLE ENGINEERING CO INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

578605107

(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): 578605107

1

Names of Reporting Persons

FMR 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 1,278,023.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,280,170.12
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,280,170.12

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)

5.0 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP Number(s): 578605107

1

Names of Reporting Persons

Abigail P. Johnson

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 1,280,170.12
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,280,170.12

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)

5.0 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MAYVILLE ENGINEERING CO INC
(b)	Address of issuer's principal executive offices: 715 SOUTH STREET,MAYVILLE,WI,US,53050
Item 2.
(a)	Name of person filing: FMR LLC
(b)	Address or principal business office or, if none, residence: 245 Summer Street, Boston, Massachusetts 02210
(c)	Citizenship: Not applicable
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP Number(s): 578605107
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: 1280170.12
(b)	Percent of class: 5.0 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Please see the responses to Items 5 and 6 on the cover page.
	(ii) Shared power to vote or to direct the vote: 0.00
	(iii) Sole power to dispose or to direct the disposition of: 1280170.12
	(iv) Shared power to dispose or to direct the disposition of: 0.00
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.
	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. One or more other persons are known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the COMMON STOCK of MAYVILLE ENGINEERING CO INC. No one other person's interest in the COMMON STOCK of MAYVILLE ENGINEERING CO INC is more than five percent of the total outstanding COMMON STOCK.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See attached Exhibit 99.
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.

FMR LLC

Signature:	Stephanie J. Brown
Name/Title:	Duly authorized under Power of Attorney effective as of January 3, 2023, by and on behalf of FMR LLC and its direct and indirect subsidiaries*
Date:	08/05/2026

Abigail P. Johnson

Signature:	Stephanie J. Brown
Name/Title:	Duly authorized under Power of Attorney effective as of January 26, 2023, by and on behalf of Abigail P. Johnson**
Date:	08/05/2026

Comments accompanying signature: * This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 10, 2023, accession number: 0000315066-23-000003. ** This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 31, 2023, accession number: 0000315066-23-000038.

Exhibit Information

Please see Exhibit 99 for 13d-1(k) (1) agreement.