This set of casters are used, but in very good shape. They came off of a tea cart. The wheels are made of shiny steel (stainless?) and rubber. They do have the ball bearings under the stems so that each wheel swivels.
Each wheel measures three inches in diameter. The distance between the base of the stem and the floor is 3 1/4 inches. The stems are 1 1/2 inches long. Sockets for the stems are available elsewhere in the catalog.