I've use castor cups to protect the floor and they work well. I googled piano castor cups and came up with several links that have them---one is below to show you what they look like--or your local piano/music store may sell them as well. They come in several styles and materials. Ours are extremely hard plastic and can have felt on the underside for hardwood. Here is a link that might be useful: Castor cups

Yes, I confess, I am a closet clean freak. I try to pretend I am not but really I can not help it. I don't love to clean, I just can't relax if I walk on a floor with even one tiny little sand grit on my foot. Even with college roomates I was the girl cleaning at 3 am. While everyone was passed out drunk. I was raised this way. You should see my sisters. We all scrub our floors on hands and knees. No one walks in our homes with shoes on. Every night before bed I wipe down the floors in the kitchen. Maids quit with me they don't get fired. : ) I must be from a long line of cleaning ladies... When I gave birth to my first child, my mother and aunts arrived. My husband was shocked to find one aunt scrubbing the sidewalk in front of our home. She bleached the steps and walkway. It was then DH realized that he married into a family of clean freaks. Sorry to go off topic. I guess this is why the felt pads work for my floor. Or maybe it is me working for the felt pads. > Boxerpups (Yes, I chase dog hair like the rest of the world)

Take a look at Slipsticks. I haven't used them yet but read about them here. They seem like a good alternative to felt pads. Here is a link that might be useful: Slipstick

I use a product called "Furniture Feet". The paper inside the box lists four sizes available: extra small, small, large, & extra large. At my local Bed Bath & Beyond store, they only have sizes small and large. Maybe the other sizes can be found online. The small is for leg size 7/8" - 1 1/4". Large is for leg size 1 3/8"- 1 5/8". The clear stretchy part is very flexible, yet sturdy. They fit round legs as well as square or rectangular legs. Furniture Feet