Feature: 1.Each product has a unique manufacturing part number label on the inner package which proves that it has been qualified, which includes part number, model number and inspection date information; 2.If you have any question about the item,please provide us the Mfg Part Number for checking,your profits will be guaranteed. 3.Made of Metal and PU material, grip ring stem type, with brake. 4.The load capacity is 30kg each caster. 5.Apply to office chair, sofa , goods shelf, sofa bed, storage rack, mechanical equipment, etc. Specification: Material: Metal+PUColor: BlackLoad Capacity: 30kg (each caster) Wheel size: 50 x 50.7mm / 1.99 x 2.00 inch (Dia x H) Grip Ring Stem: 11 x 20mm / 0.43 x 0.79 inch (Dia x H) Please allow 1-5mm error, we measure it manually. Weight: 400g Package included: 4 x chair casters