The 12 1/2 x 2 1/4 Electric wheelchair rear wheels’ main material is polyurethane foam. Its max load capacity is around 75kg per wheel. The polyurethane tires are produced chemically, a number of variations are possible. The density and physical characteristics of the material can be modified according to the end use, so if u have any special requirement, we can custom the wheels for u.
link:http://www.pu-tire.com