Description A lot of Hummer H1’s have cooling issues and the factory has made many upgrades over the years.  We are just taking it one step further.  To help engine coolant temperature, the factory replaced the single thermostat housing with a dual thermostat housing to increase the flow to the radiator.  The engine coolant will take the path of least resistance; therefore we are increasing the resistance for the fluid to short cycle and bypass the radiator.  This will make a larger percentage of the coolant actually travel through the radiator and therefore reduce engine coolant temps. BRF (Bypass Restrictor Fitting) replaces the factory water pump bypass fitting.  The BRF is made of 100% stainless steel and is machined in Texas.