Material :SOLID HARD WOOD - real black walnut, sapele,zebra,rosewood / jacoranda, oak wood for options Protection for Piano Wheels - Protects metal and brass wheels from rust or tarnish Designed for Upright Pianos - 4 pcs in a set of package. Protect Floors and Carpets - Underside of each cup is lined with felt pad for floor protection as well as sound insulation and antiskid. Natural Wood Grain Difference - There is a little different on color each cup, this is normal because of the real wood grains.