1Dual Pressure Unit: Dual pressure unit up to 300PSI or 20BAR with large easy to read dial, acrylic glass cover with scratch resistant coating and rubber protective cover with excellent shock absorption. 2Builtin Check Valve: Builtin check valve with pressure holding function ensures that the pressure gauge obtains the maximum pressure of the spark plug during the compression process. 3Professional and Durable: Compression tester tools are made with the Abs ,rubber and brass components, built for all day performance in the shop or garage. 4Multiple Adapters: Equipped with different sizes of rotating and push in adapters, widely used in most types of gasoline gas engine cylinders and deep spark plugs, common in motorcycles, lawn mowers, cars, trucks etc. 5Test Presure: Used to quickly and accurately test the cylinder pressure of gasoline engines. Can help diagnose stuck valves, carbon deposits, broken cylinder heads or defective main gaskets, poorly installed or worn piston rings, burnt or damaged pistons, etc.