This 331 Number 4 Pneumatic Damper Actuator with non-pivot mounting screws 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, is front mounted and has a replaceable diaphragm. This actuator has an air connection of 1/8" NPT female with a dual barb elbow fitting for 1/4" OD tubing.