Includes: Comp main body Recoil spring Guide rod Guide rod fitment washer Guide rod head Internal spring Warning card. The Mass Driver Compensator is driven by the hot gasses expelled through the barrel after the round is discharged and acts as a counter balance system to attenuate mechanical recoil. Barrel mounted compensators add reciprocating mass and increase the moment of inertia to the operating system which can have a negative effect on reliable cycling of recoil operated handguns. By separating the compensator from the operating components after ignition the MDC allows for close to stock cyclic speeds and reduces reciprocating mass.