This Billet Style Cast Aluminum Fluid Control Thermostat with 3/8 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. Hardware kit with brass fittings and hose clamps included.