Wolf Tooth Headset Spacers for Trek Knock Block are machined in the USA out of aircraft-grade aluminium. Available in a variety of colours to match the style of your bike.
These spacers are to be used only with Trek Knock Block system. They are not compatible with other bikes.
Trek developed Knock Block as an integrated frame protection system to prevent self-inflicted scuffs, dents, or cracks from spinning handlebars. Knock Block consists of a special stem and a stop chip on the frame. The stop chip limits the turning range of the custom keyed headset cover. The top of the headset cover has notches that lock into corresponding notches on the headset spacers, which also correspond with notches in the stem for a strong connection to the steer tube. These parts work together to prevent the crown of the fork and handlebar controls from hitting the frame when bars are turned too far in either direction.