Gravity Ventilator, Blade Dia. 54 In., Base Square Size - Roof Ventilators 60-1/2 In. x 60-1/2 In., Style - Roof Ventilators Low Profile, CFM/Throat Velocity @ 0.050-In. SP Gravity Intake 10,851/457, CFM/Throat Velocity @ 0.050-In. SP Gravity Relief 12,094/509, CFM/Throat Velocity @ 0.100-In. SP Gravity Intake 14,934/629, CFM/Throat Velocity @ 0.100-In. SP Gravity Relief 17,103/720, CFM/Throat Velocity @ 0.125-In. SP Gravity Intake 16,697/703