A bike headset is a small vital piece of bike component used to provide a surface on which the bicycle fork can be rotated by the handlebars. The headset serves as a rotatable joint between the fork and the head tube of the main bike frame. Bike headsets typically consist of two cups – a top cap and a bottom cap. The bottom cap is pressed at the bottom of the headtube, while the top cap is placed on top of it. Inside these cups are ball bearings, which allow smooth and low-friction rotational movement.
Like other bike parts, there are many types of headsets. There are threaded headsets, threadless headsets and integrated headsets. One of the recent designs is the internal headset, or sometimes called semi-integrated headsets. The internal headset consists of all the parts of the conventional headsets, except that the bearings are inside the head tube, instead of outside. According to reviews, the popular brands of internal headsets are Chris King Headsets’ InSet and Cane Creek ZeroStack. These headsets are used for head tubes with 44m internal diameter.
As mentioned, the bearings in the internal headset do not touch the frame; they instead make contact with the steerer tube inside the head tube. These bearings are contained by a cup or shims made of aluminum or plastic. However, before using a Chris King headset or any brand of headset, keep in mind that the bike frame has been designed for specific type of headset. So you cannot use an internal headset if your frame is designed for conventional types.