A thermoplastic top race is used instead of traditional aluminum. An O-ring seal protects the top bearing cartridge from contamination, while the lower cartridge is kept clean by a high pressure, low friction lip seal. Both top and bottom bearing cartridges are double sealed. Pop them out once, and you'll be replacing them. Race Face designed the Thermo SP to require no periodic relubing.
Bearings come packed with the optimum amount of waterproof grease from the factory.
Installation of the Thermo SP was a breeze. Our local mechanic popped the headset uneventfully into a test bike's head tube. We've been riding and racing the Thermo SP for a couple months now through all conditions. It's action has been flawless. We confidently recommend the Thermo SP to potential buyers.