Wolf Tooth Headset Upper Knock Block - 28.6 8mm Red. Wolf Tooth Precision Headsets for Trek Knock Block are machined in the USA out of aircraft grade aluminum with superior sealing for protection against the elements. Available in a variety of colors to add some style to your bike. These upper headsets are for Trek frames with molded-in internal bearing cups.

Designed to work with Treks Knock Block system

The top cap on these headsets have unique raised features that key to Knock Block compatible stems (made by Bontrager

If spacers are needed you will need to use special Knock Block compatible spacers with notch features

This product is the upper headset only

Lower headsets on bikes with Knock Block do not have any unique features. They are usually IS headsets which are available separately