I'd give this product 5 stars except the directions are factually wrong.  If you buy this, please be aware that the directions call for spring washers on all of the bolts.  The hardware package is short 4 spring washers.  Omit these from the bolts that attach the chair to the swivel and you'll be fine. If the chair wobbles a bit (two of mine did),determine which two legs are the long ones.  Turn the chair upside down and use a hammer to tap the floor protectors in a bit. Problem should be solved.