The Alvin CK59 Chair Height Extension Kit consists of cylindrical steel shafts, tapered to lock into the chair base and extra-strong foot rings. This extension kit adds approximately 7-1/2" to the height of the chair. Foot rings can be adjusted vertically and then locked at the desired height. It has 21" diameter, black powder coated foot ring and black spokes. This CK59 Chair Height Extension Kit fit the following chair models CH444, CH555.