The size of the BMX wheels are close to standard
The BMX wheel is made from 4 different components; rim, spokes, nipples and wheel hub.
The rim is a hoop shaped metal construction and holds the tire and the tube. The nipples connect the spokes to the rim. The spokes connect the rim to the hub, and the wheel hub makes the wheel able to spin.
Even though BMX wheels are produced from 12”-20” the most common size for race BMX wheels are 20”. The sizes 12”-18” are mainly produced for children and young teenagers.
Notice: It is important when changing wheel hub that the spoke hole count is the same as on the rim - 36 and 48 holes cannot be mixed.