Benchworld’s Premium X-Large Solid Wooden Caster Cups, with a polished ebony finish, are the ideal choice for foot protectors for grand piano. They feature a new design with three ripples on each side and a wider inner diameter to accommodate larger wheels. The outer diameter measures approximately 5.5 inches, while the inner diameter is 4.25 inches. This set includes three cups along with a black adhesive felt. The felt facilitates easy sliding, whereas rubber can make it more challenging to move the piano.