26" Replacement Aluminum Chair Base Standard 2" center hub hole to receive most standard chair gas lift cylinders Standard 7/16"x7/8" (11mm x 25mm) sockets to receive most standard caster mounting stems This heavy duty polished aluminum chair base can be used as a replacement for chairs and stools with a standard 2" wide gas lift cylinder. It works on most chairs purchased at office supply stores. It can also be used to replace standard black plastic bases, giving your chair a nicer, more finished look