The demands placed on a piston seal depends greatly upon the operating conditions for which they have been chosen. Bore surface finish, hydraulic fluid type, contamination, application cycle rate and speed, pressure, and temperature are just a few of the factors that can help determine what kind of seal is right for a given application. Unlike a rod seal, where leaking of hydraulic fluid is not acceptable, a small amount of leakage in piston area is generally seen as desirable. This small amount of fluid acts as a lubricant for the piston seal during operation. Piston seals, both single- and double-acting, can be designed for use with integrated or separate back-up or guide rings.