• Measures cylinder compression to accurately diagnose engine condition Compatible with most standard spark plug threads Quick disconnect coupler separates hose from gauge for faster,easier connections to the engine Push button side release valve allows repeated testing without disconnecting Includes adapters for most standard spark plug threads: 10mm,12mm, 14mm, 4mm long reach, 18mm Repair kit includes valves and rubber O-rings Easy-to-read, 2-1/2" professional gauge Bourdon tube movement for accurate readings Heavy-duty rubber boot protects gauge Standard and metric scales: 0-300 lbs psi and 0-2100 kPa Tool pouch keeps parts organized