Wolf Tooth Performance Headset - IS41/28.6 Upper 7mm Stack Ultraviolet PurpleWolf Tooth Performance Headset IS41 28. 6 Upper 7mm Stack Ultraviolet Purple. Wolf Tooth Performance Headsets are machined out of aircraft grade aluminum and assembled with Black Oxide Cartridge Bearings balancing quality and price. Black Oxide Bearings are made from chromium steel for high load capacity durability and corrision resistance Ultralight stem cap with integrated spacer plus an aluminum bolt and a star nut O ring seal prevents water