X0508 4 2026-03-15 0001766368 Mayville Engineering Company, Inc. MEC 0001751718 Lehr Rachele Marie 135 SOUTH 84TH STREET SUITE 300 MILWAUKEE WI 53214 false true false false Chief Financial Officer false Common Stock 2026-03-15 4 M false 8560 0 A 29321 D Common Stock 2026-03-15 4 M false 5808 0 A 35129 D Common Stock 2026-03-15 4 F false 4600 16.67 D 30529 D Restricted Stock Units 0 2026-03-15 4 M false 8560 0 D Common Stock 8560 8560 D Restricted Stock Units 0 2026-03-15 4 M false 5808 0 D Common Stock 5808 11614 D Restricted Stock Units 0 2026-03-15 4 A false 16497 0 A Common Stock 16497 16497 D Stock Option (right to buy) 14.12 2033-02-28 Common Stock 24814 24814 D The restricted stock units will vest 1/3 on each of March 15, 2025, 2026 and 2027. The restricted stock units will vest 1/3 on each of March 15, 2026, 2027 and 2028. The restricted stock units will vest 1/3 on each of March 15, 2027, 2028 and 2029. The options will vest 50% on each of February 28, 2024 and February 28, 2025. Garrett F. Bishop, Attorney-in-Fact for Rachele M. Lehr 2026-03-17