Powerbuilt 647000 Compression Tester Designed for fast and accurate compression testing of gasoline powered engines. Fits both 14mm and 18mm spark plug threads. Meets or exceeds ANSI standards. Lifetime warranty. Fits both 14mm and 18mm spark plug threads Meets or exceeds ANSI standards. Checks cylinder compression from 0 to 300 PSI Fits 14 and 18 millimeter spark plug threads Equipped with air-hold valve and gauge reset button 11 inch Flexible rubber hose