Abstract: A fluid pressure actuator consisting of piston structure reciprocal within a cylinder pressurized through ports at the cylinder ends wherein cushioning means is mounted upon the piston structure controlling the flow of fluid through the ports producing controlled piston deceleration at the termination of its stroke. The port utilizes sealing means in the form of a radially expandable and contractable sealing ring floatably mounted to permit limited radial and axial movement. The seal ring closely engages, in a telescoping manner, the outer cylindrical surface of a valve member mounted upon the piston structure wherein a very accurate and effective seal occurs between the ring and valve member, and bleeding of the cylinder chamber being exhausted can be accurately regulated by predetermined flow control apparatus such as slots, orifices or adjustable needle valves.