The Safco Uber Short Pneumatic Cylinder 3489NC replaces the standard pneumatic cylinder on the Safco Uber line of chairs (model numbers 3490 and 3491). This replacement cylinder reduces the seat height adjustment to 17” to 21”, for people who want a shorter chair. It is made of steel with a black finish and a black nylon covering. Outside dimensions are 2” diameter x 12½”-20½”L. Some assembly is required.