The Hickok/Waekon Back Pressure Tester, No. BPT02, allows techs to quickly test back pressure and clogged or obstructed catalytic converters. A three-stage adapter has 12mm and 18mm thread sizes to fit most domestic and import vehicles oxygen sensor ports. The standard 1/4"-20 tip provides the ability to test through the exhaust pipe when O2 sensor ports are inaccessible. High temperature silicon hose prevents damage to tester from high exhaust temperatures.