The VPC unit and setup unit of a graphics processing subsystem perform culling operations. The device includes a base, a pair of clamping members, with one of the clamping members being movable away from and toward the second clamping member. The service cart comprises features that prevent or minimize damage to the service cart, or to an object struck by the service cart, when the service cart engages another object. Another embodiment of the reactor comprises a dual piston configuration having CO2 and H2 active membrane pistons inside a single cylinder.