This Billet Style Cast Aluminum Fluid Control Thermostat with 1/2 inch NPT ports allows the oil to bypass the cooler until it reaches 180 degree F at which point the internal thermostatic valve will close and force 100 per cent of the oil through the cooler while maintaining a constant pressure system. This process allows the engine/transmission to achieve the ideal operating temperature quicker before passing the oil through the cooler. The unit can be rotated 180 degree to change flow direction.