The Hiddenset headset is integrated into the head tube of the frame, conferring an extremely elegant look to the bicycle. Light, smooth, long lasting and easy to install. Hiddenset internal headset, requires head tube designed for internal headset 42mm head tube I.D. Includes top cap assembly Steerer Tube-1-1-8 Threadless Headset Type-Integrated, 42.0mm OD bearing (Hiddenset) Crown Race-30.0 Stack Height-5.9 mm Bearing Type-1-8 Ball Material-Al