For use with our CT-101 and CT-104 wooden wheel casters as well as other casters with a ball tip stem, CT-115S is inserted in the hole in the bottom of the leg and tapped in to secure. The caster stem then slides up into the stem to lock it into place. The stem is 1 1/4" long and is 3/8" in diameter. The base is 3/4" in diameter. The sockets are made of raw steel and will rust if not coated with a lacquered or other product. Caster leg inserts or stems are sold individually.