CRUSHPROOF Straight Adapter fits single tailpipes with an OD up to 3", adapting to 3.5" ID hose. CRUSHPROOF tailpipe adapters are designed to protect the hose and tailpipe, and dynamometer hoses and adapters are formulated to withstand the high temperature of a dynamometer, with a heavy wall thickness that increases durability. Always select an adapter with at least 1/2" diameter clearance around the tailpipe.