BVVT SF6S 6CFM Two Stage Spark Free Vacuum Pump This is the BVVT SF6S 6CFM Two Stage Spark Free Vacuum Pump Please Refer to these charts for vacuum specifications at altitude and conversions: Vacuum at Altitude Chart Vacuum Conversion Chart Key Features: Internal Check Valve Spark Free Construction Oil Mist Filter Cap Larger Oil Reservoir for longer Oil life Lightweight Rubber Feet for noise dampening Reliable, Economical and Efficient.