This tester is the superior dual gauge design. It has an adjustable left-hand gauge with a precision regulator and a large easy to read right hand gauge. Comes with an aluminum black anodized main body, corrosion resistant solid brass coupler, and a hose for 14mm plug holes. This tool enables the professional engine builder/tuner a way to pinpoint leakage of the piston bore, rings, valves, heads, and gaskets without taking the engine apart. With an adapter it can be used to set injection barrel valves. Much more versatile than a simple compression gauge.