8milelake Engine Cylinder Leakdown Tester Dual Gauge Diagnostic Kit TU-21 Cylinder Leak Tester Designed to detect a variety of common engine faults including: Worn piston rings, worn valves, cracks in cylinder walls and blown head gaskets. Suitable for use on any petrol engine with 12 or 14mm spark plugs. Tester checks the amount of leakage in an engine cylinder & helps determine the source. Ideal for testing trucks & late model cars where clearance is minimal.