The headset is the set of components on a bicycle that provides a rotatable interface between the bicycle fork and the head tube of the bicycle frame itself. There are a few types of headset, these are threaded and ahead. Threaded headsets are the older type and use a thread on the forks steerer to adjust, an ahead type has no thread and uses a top cap to adjust the tension. Ahead headsets come in three options, external cup, internal and integrated. Integrated and internal headsets use bearings which fit inside the headtube and provide clean lines, whereas the external cup system uses cups which fit into the frame but are still visible. Most will use cartridge bearings which last well and have very low maintenance requirements, one thing worth doing is to switch the top and bottom bearing periodically, as the bottom bearings are more prone to wear as they support the weight of the bike and rider.