X0407 4 2023-04-18 0001766368 Mayville Engineering Company, Inc. MEC 0001705018 Rothman Jay O. 715 SOUTH STREET MAYVILLE WI 53050 true false Common Stock 15000 D Director Restricted Stock Units 0 2023-04-18 4 A 0 9721 0 A Common Stock 9721 9721 D Director Deferred Stock Units 0 Common Stock 14485 46135 D The restricted stock units will vest 100% on the date of the 2024 Annual Meeting of Shareholders. The balance includes vested RSUs that were deferred by the reporting person, which will be settled upon the reporting person's retirement or separation from the company. /s/ Russell E. Ryba, Attorney-in-Fact for Jay O. Rothman 2023-04-19