Derale 25011 Fluid Control Thermostat Kit It allows the oil to bypass the cooler until it reaches 180 degree farenheit at which point the internal thermostatic valve will close and force 100% of the oil through the cooler while maintaining a constant pressure system. Bypasses cooler at 180F Provides quicker warm-up temperatures Perfect for cold weather climates Can be rotated 180 degree to switch flow direction