Siemens 331-4813 DAMPER ACTUATOR, PNEU, NUMBER 3, 2-3/8" STROKE, 8-13 PSI, FIXED BRACKET MOUNTSiemens 331 4813 Damper Actuator, Pneu, Number 3, 2 3 8" Stroke, 8 13 psi, Fixed Bracket Mount This 331 Number 3 Pneumatic Damper Actuator is a rugged, metal fabricated device that provides gradual or positive actuation of HVAC dampers. This actuator has a nominal spring range of 8 to 13 psi, is fixed bracket mounting and has an ozone resistant rolling rubber diaphragm. This actuator has an air connection of 1 8" NPT female with a straight dual barb