Product Description ✅ Application: It used with diesel compression tester TU-15. Insert the M10-1.25 threaded adapter quick disconnect screws into the glow plug hole in the head of the engine. Fits for 6.6L Diesel Duramax engines, 2005 to present. ✅ Function: This test adapter used with diesel compression tester TU-15, mainly used to measure the maximum pressure generated in the compression stroke of the diesel engine cylinder. Specially designed to check the compression pressure of gas in the cylinder. .