Checks cylinder compression from 0 to 300 psi (0-21 Kg/cm2). Adapters fit 14mm and 18mm spark plug holes. Special air hold valve for easy resetting of gauge. 16" rubber hose. Serviceable product Need to know if an engine has a problem? Whether you're buying a used vehicle or trying to decide whether to rebuild a motor, a compression tester comes in handy. The KD Tools Compression Tester can let you know if you've got worn rings, a blown head gasket or other cylinder compression issues. Made for everyday use!