"This 331 Number 4 Pneumatic Damper Actuator with integral pivot and pivot post is UL recognized for fire and smoke applications and is a rugged, metal-fabricated device that provides gradual or positive actuation of HVAC and fire/smoke dampers. This actuator has a nominal spring range of 8 to 13 psi, a replaceable diaphragm and an air connection of 1/8"" NPT internal threads with a dual barb elbow fitting for 1/4"" OD tubing. Also included is an universal mounting kit that allows fixed or pivot mounting, this kit contains parts for frame mounting."