Compatible with direct & indirect petrol engines which have 10, 12, 14 or 18mm spark plug threads. It acurately detects common engine faults such as worn piston rings, worn valves, cracked cylinder heads & blown head gaskets. Twin gauges indicate both cylinder pressure 0-100psi/0-7BAR & percentage of cylinder leakage. Both gauges are fitted with heavy duty rubber protectors. Supplied in a plastic storage case.