Blower Relief Valve Vacuum Capabilities Pressure Preset Limit 166 in wc Outside Diameter 6.9 in Inlet Size 3 in Inlet Type NPT Compatible Manufacturer Part Number 53WC17 53WC18 Compatible Grainger Part Number 53WC17 53WC18 Maximum Operating Pressure 15 psi Minimum Operating Pressure 1 psi Overall Length 8.7 in