Features: 1. APPLICATION: The hpop test gauge tool is compatible with 1994-2007 Ford Powerstroke 6.0L & 7.3L Diesel engines, 1994-2007 International VT365 & T444E Diesel engines, 1997-2006 CAT 3126B, 3126E, and C7 Diesel engines. 2. FUNCTION: Dual purpose test tool, monitoring system performance with the analog gauge or testing air leak. Check the leak in the engine's high-pressure oil system that runs fuel injectors, and find the precise source of leakage. Save your time and your money. .