Rolland Office Chair Caster Wheel for Hardwood Floor - Stem Diameter: 9.5mm, Stem Length: 25mm - 5 Unit/Pack RollandTM Polyurethane Material - Made specifically for use on all Hardwood, Hard Surface Flooring Stem diameter: 9.5mm - Fit older/ikea/non-standard chair base Practial solution compare to space restricted chair mat Tested to ANSI/BIFMA Safety Standard