A BMX headset consists of components which provide a rotatable interface on your bmx bike between you bikes fork and head tube of the bike frame. A typical headset has two cups pressed into the top and bottom of the head tube. There are bearings inside the 2 cups which provide a low friction contact between the bearing cup and the steerer. Headsets come in a few different applications for bmx bikes, so be sure of the size needed. Headset colors and styles vary so be unique while you are replacing or upgrading your bmx headset.