Woodi Hardwood Piano Caster Cups WPA-9 Set of 3 Wood Black 5.25" Designed for use with pianos Made of High-Quality Select hardwood, 3 cups in 1 package. Protects wood, tile, and carpet from piano caster damage Dimensions: 5.25" - outside diameter, 2.75"- inside diameter Underside of each cup is lined with felt pad