Made from die cast aluminium w/ silicone sealant for a tight fit and prologned service life. Deep fins with large surface areas help to dissipate heat better. High quality shaft and bearings to reduce slipping and ensure long, reliable lift. Bi-static springs adjusts fan speed according to requirements, saving you fuel Dayco Fan Clutches are die-cast aluminium and have a machined body that helps to provide for a tight fit within close tolerances, while producing precision performance. Deep fins increase surface area for improved heat dissipation, while exclusive drive spines are knurled and burnished. The shaft surface resists slippage caused by heavy torque loads and assures longer bearing life. Top-quality bearings ensure longer life and quiet, smooth running. A special silicone fluid inhibits heat build-up to prolong service life. A bi-metal thermostatic spring adjusts the fan speed in response to operating temperature requirements - reducing fuel consumption.