30 Gravity Ventilator

Item: Gravity Ventilator, Low Profile, Fan Size:30", Damper Size:31" X 31", Base Dims:34-1/2" X 34-1/2", CFM/Throat Velocity 0.050-In. Sp Gravity Intake 3153/504, CFM/Throat Velocity 0.050-In.
Sp Gravity Relief:3646/583, CFM/Throat Velocity 0.100-In. Sp Gravity Intake:4459/713, CFM/Throat Velocity 0.100-In. Sp Gravity Relief:5156/825, CFM/Throat Velocity 0.125-In. Sp Gravity Intake:4985/798, CFM/Throat Velocity 0.125-In. Sp Gravity Relief:5765/922, CFM/Throat Velocity 0.200-In. Sp Gravity Intake:6306/1009, CFM/Throat Velocity 0.200-In. Sp Gravity Relief:7292/1167, CFM/Throat Velocity 0.250-In. Sp Gravity Intake:7050/1128, CFM/Throat Velocity 0.250-In. Sp Gravity Relief:8153/1304, Construction Material: Galvanized Steel, Overall Dims:38"H X 57"W X