These Madico caster sockets make it easy to install stem-mounted casters onto your furniture. The sockets are easily inserted into a frame or legs to accommodate casters, which makes your furniture easier to move and provides improved weight distribution in order to protect your flooring. The caster sockets feature a white finish and a round design, and they are made of polypropylene for lightweight durability. They have a 1/2" (13 mm) outside diameter and a 5/16" (8 mm) inside diameter. The package conveniently contains 4 caster sockets.