Sorry, I didn't look up the name of the product that I was thinking of. I looked in Van Dyke's 2001 Fall catalog on page 173--the page after the last page of available caster styles they have-- and saw that they are called Glass Coasters or Rubber Coasters. The rubber ones are very inexpensive ($2/set of 4) and come in square or round styles. The glass ones--made for chair legs and casters, not drinking glasses--are around $8/set and come in different colors of glass and size. I have also seen metal coasters in hardware stores that are for the same use. The metal ones are usually painted the most unattractive brown color imaginable. The metal ones also tend to rust over the years and can mark your floor that way so the glass or rubber ones are better. All of these still do the job of spreading the weight from one contact point for a caster or glide out over an area of up to 3" around.