uxcell Plastic Dual Wheel Grip Ring Chair Swivel Brake Caster 11mm Stem 2pcs Main Material: Plastic, Metal; Package Content: 2 x Grip Ring Stem Caster Wheel Product Name: Grip Ring Stem Caster Wheel; Weight: 174g Main Color: Black, Silver Tone; Overall Size: 82 x 67 x 50mm/3.2" x 2.6" x 2"(L*W*H) Wheel Size: 50 x 15mm/2" x 0.6"(D*T); Type: 360 Degree Rotation,Dual Wheel,Brake Lock Stem Dia: 11mm/0.43"; Stem Length: 20mm/0.8"