Air cylinders are pneumatic linear actuators driven by pressure differential in the cylinder chambers. One side of a piston flange can be pressurized to provide force and motion with a spring (providing return force after pressure is released), or both sides can be alternately pressurized for bi-directional powered motion. Air cylinders are used in many positioning, actuating and clamping applications. Choices for air cylinder style include tie rod, smooth body, pancake, rectangular, rotating and multiple bore. Tie rod cylinders are held together by exterior tie rods, and are usually in a rectangular bolt pattern. In a smooth-body air cylinder, the cylinder’s body encases the piston. A pancake cylinder has a shorter length and larger diameter than other air cylinder styles. A rectangular cylinder is encased in a rectangular, box-shaped frame. In a multiple-bore cylinder, two or more bores and pistons combined or stacked in same air cylinder. The cylinder can be single or double action. In a single-action device, the cylinder contains pneumatic porting for drive in only one direction. Single-action air cylinders frequently incorporate a return spring to the unpowered position. In a double action device, both sides of the piston can be pressurized for reversible motion. Force ratings can differ somewhat in opposite directions.