4" x 1-1/4" Mold-On Rubber Aluminum Wheel Swivel Caster - 250 lbs. capacity4" x 1 1 4" Mold on Rubber Aluminum Wheel Swivel Caster The mold on rubber aluminum wheel is a lightweight alternative to the traditional cast iron core, providing the same load capacity with a cushioned tread and an attractive look. Tread: Rubber Vulcanized To Core Core: Aluminum Bearing: Annular Ball Bearing Rig: Zinc Plated Swivel Caster, 2 3 8" x 3 5 8" Mounting Plate Capacity: 250 Lbs. Color: Gray and Non marking Durometer: Shore A 80 (+ 5)