Cylinder Actuators

Or
piston actuators
Piston actuators utilize a piston with an o-ring or quad ring seal within a cylinder.
Air can be supplied to both sides of the piston to provide the actuator force in either direction, these are said to be double-acting actuators.
A piston actuator may also utilize a spring to replace the air on one side of the piston or to provide additional force with the air.