The R5X2CSTR is an upgrade caster for the R8RT and R10RT. The custom-designed R-Trac wide wheels feature low profile no-flat tires, lightweight but strong polymer hubs, low rolling resistance, pneumatic-like cushioning, vastly wider load dispersion over soft terrain, and a stunning racing-style look. 5 x 2 Brake casters are 50% wider than typical casters and can Glide over soft terrain. All casters are sold individually, but you must purchase (2) for use as an upgrade to the R8RT & R10RT.