NOTE: The ATS 2E Differential Pressure Tester has a .040” orifice and is the appropriate tool for ALL Textron Lycoming engines as indicated in their Service Instruction SI-1191A. Teledyne Continental engines require our model 2EM to comply with their Service Bulletin SB03-3. For all other makes of engines, consult FAA AC43.13 REV 1B for guidance in selecting the proper instrument for your engine. Our own differential pressure tester comes complete with on-off safety valve to eliminate pressure when disconnecting from the cylinder. Can be used to check intake or exhaust valves, cracked or worn rings, defective cylinders, worn bushings, etc. Specifications: Orifice size is .040". precision gauges matched to within +/-2%. Includes 18MM Spark Plug Adapter, 24" pressure hose, and complete instructions. Protective form-fitted hard case included. Factory calibrated. Letter of certification available upon request. 2 lbs (1Kg) shipping weight.