Shepherd Hardware 9389 Poly Rigid Wheel Caster, 5 x 2 inchesLong wearing, low cost, lightweight and non marking wheels with good chemical resistance, impervious to water for most general medium heavy duty industrial applications such as platform trucks, wire shelving, and other warehouse trucks and carts for commercial use. Use in acid, oil, or water, and on carpet or concrete. Top plate made with 1 4" cold forged steel. Wheel bearings are straight roller 3 4" with spanner bushing. 4 1 2" x 3 15 16" square