I love these things. I will carry a pair in my pocket when I go out to a bar, or even a concert. Most shoes have grippy soles nowdays and that's just plain hard on my knees. These work on most floors, including carpet. They will get sticky if you step in a spilled drink, more so than leather soles, but that's fine. They are small enough to carry a spare pair in my jacket.

They won't work on rubbery floors, like I've seen in some yoga places. Outdoor concrete will tear them up pretty fast, though they work fine on smooth indoor concrete floors.