Abstract: A pressure-driven cylinder having a piston sliding within a sealed housing chamber between a pair of opposed side-end walls in a piston chamber. At least one chamber wall has a moveable portion of an end wall integrally connected to and axially spaced away from a pressure-driven face of the piston by an integral connector point that is much smaller in area than the piston's pressure face. That moveable wall portion acts as an integrally connected piston follower that has its own extended surface area that is progressively introduced into the presure chamber as the piston slides in order to reduce the required volume of pressurized driving fluid in the piston chamber. A chamber for the follower itself is sealably isolated from the piston chamber so that no driving fluid backs into the follower chamber. Both the end wall/follower and the piston reciprocate together.