Thermostat Housing Bolt Kit, Hex Head S/S AR434-7402Thermostat Housing Bolt Kit, Hex Head S Sfits GM LS Series 20mm UHL AR434 7402 434 7402 Nobody likes water leaks. And here's ARP's contribution to the solution. These premium grade bolts are engineered to properly engage the manifold threads and resist loosening. They're application specific, and come in your choice of black oxide finished chrome moly or rust proof stainless steel, with handy 12 point or standard hex heads. Washers included.