niceeshop 1 X (TM) 2" Twin Swivel/Office Chair Wheel/Fixed Type Replacement Caster Roller -Black Material:Plastic,Metal Connector; Size:1.1x2.3cm / 0.43 inchx0.9 inch(DxL) Wheel Diameter:5cm/1.96inch Standard Stem Length:7/8 inches / 22mmStandard Stem Diameter:7/16 inches / 11mm 360 Degree Swivel Rotation,fits all office chair bases with 7/16 inch (industry standard) mounting holes