Caster cups help protect your hardwood flooring or carpeting from indentations from the weight of the piano.
These piano caster cups are made of clear Lucite. They measure 4-1/2" outside diameter and 3" inside diameter.
Check out our blog for help in choosing the right caster cups for you:
https://intunepianosupply.com/blogs/piano-basics/what-are-piano-caster-cups-and-why-are-they-important