I have been asked by a number of people "what size bearing" they need in their KCNC F13 headset. This is the headset most commonly used on the Travers RUSSTi, RUDY, RUDY Fat, Fat Race and Bat Fastard. They are:
The top headset bearing is: PT-R408
The Bottom Headset Bearing is: PT-R413
HAND BUILT TITANIUM FRAMES.