Mayville Engineering Company, Inc.

10b5-1 Trading Arrangements

On December 16, 2025, Jagadeesh A. Reddy, President and Chief Executive Officer, adopted a Rule 10b5-1 trading arrangement. Mr. Reddy’s trading plan provides for the potential sale of up to 56,078 shares of the Company’s common stock subject to vesting of the Company’s restricted stock units until March 15, 2028. This trading plan was entered into during an open insider trading window and is intended to satisfy the affirmative defense of Rule 10b5-1(c) under the Securities Exchange Act of 1934, as amended, and the Company’s policies regarding transactions in the Company’s securities.

During the three months ended December 31, 2025, no other director or Section 16 officer of the Company adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408 of Regulation S-K.

Discretionary Cash Bonuses

On March 2, 2026, the Compensation Committee of the Board of Directors of the Company approved a one-time cash bonus for certain executives, including Messrs. Reddy, Raber, Leuba, Nichols and Ms. Lehr, in connection with their successful completion of the acquisition of Accu-Fab in July 2025. The cash bonuses were awarded in recognition of the officers’ diligent and extraordinary efforts and contributions in securing a strategically significant, immediately accretive transaction for the Company and its shareholders.

The Compensation Committee approved awards, payable as soon as practicable, of $370,000, $170,000, $165,000, $105,000 and $150,000 to Messrs. Reddy, Raber, Leuba, Nichols and Ms. Lehr, respectively. These awards were considered a special, one-time bonus and not part of the Company’s annual incentive awards.