Abstract: An improved fluid cylinder including a housing defining a cylinder bore and having aligned piston rod openings at opposite ends thereof, which openings are nominally coaxial with the bore. A piston rod is within the bore and extends through both of the openings and a piston is located within the bore and includes a central opening receiving the rod and having a shape complementary to that of the rod while being slightly larger than the rod so that the piston may move radially on the rod. Securing elements are provided for fixing the axial position of the piston on the rod and include an annular shoulder abutted by the piston. A seal is interposed between the piston and the shoulder to preclude leakage of the working fluid therebetween. The relative radial movement of the piston on the rod compensates for lack of precise concentricity of the bore with respect to the rod receiving openings.