Strike Industries Mass Driver Comp, 9MM, For Glock 17 Gen 3, Includes Recoil Spring/Guide Rod/Guide Rod Fitment Washer/Guide Rode Head, Black SI-G3-MDCOMP-S The Strike Industries Mass Driver Compensator (MDC) represents a quantum leap in compensator design. Current designs have largely been unchanged since the 1930s. It's about time for something revolutionary. The Mass Driver name is inspired by the idea of theoretical mass driver engines in space travel. By ejecting mass" an equal and opposite reaction is generated propelling the space vehicle forward.