Benchworld’s Premium Solid Wooden Caster Cups are the best choice for a grand piano. The new design has three ripples on the side and a wider inner diameter for the wheel.

• Medium: The outer diameter is about 4″ and the inside diameter is 2.5″. 
• Extra-Large: The outer diameter is about 5.5″ and the inside diameter is 4.25″. 

Moreover, this item comes in a set of 3 with black adhesive felt. The felt will be easy to slide whereas the rubber makes it harder to slide the piano.

Features

• Size: Medium or Extra-Large
• Color: Polished Ebony
• Felt installed under to avoid scratches on your hardwood floor
• Inner Diameter: 2.5″ / 4.25"
• Outer Diameter: 4″ / 5.5"
• Excellent for grand pianos with smaller or standard wheels
• Set of 3