I had posted this item before and it is a set of torx sockets that is available at your local Autozone store. This is what I had used to replace my thermostat last winter. One word of advice...when you put back the two bolts to fasten down the thermostat housing, use finger tightened method first before you use the socket wrench. Just a precaution from cross threading that aluminum thermostat housing unit. The Sear's torx socket is too big to use and gets in the way of thermostat housing cover.