You have seen them on school chairs. You have seen them cafeteria chairs. They are the little plastic things that go on the bottom rails of chairs.
Do you know what they are called? They are called plastic chair glides.
These chair glides prevent floors from getting scratched. They work even better when they have felt on them.

I discoered a company that sells and manufactures these plastic chair glides. They are called LCS Products or chaircaps.com
They have to be the cheapest place around for these amazing chair glides. However there is minimum order.
If you are a school looking for chair caps and glides check out LCS products.