The Lisle HD Thermostat Seal Installer, No. 35650, is designed for use on CAT, Cummins and Detroit Diesel engines (Class 7 and 8 trucks). The double-sided centering bushing guides the seal driver so that seals can be installed straight into the recessed port in the thermostat housing. For seals without a stop flange, the handle provides the stop to install the seal to the correct depth in the housing, the company says.