Robinair 15121A Two Stage Vacuum Pump 10 CFM is designed with a two-stage pump to create a deep vacuum pull in addition to offset rotary vanes to further enhance the vacuum. The Robinair 15121A features a gas ballast to help reduce moisture condensation in the pump oil, 1/4 turn "Iso-valve" to isolate the pump from the system, built-in check valve to prevent the oil from being sucked into the system during a power loss, a durable yet lightweight aluminum housing, and more.