Conversion Chair Base Kit for Aeron Chair to Aeron Stool (Casters for Hard Floors) This is a conversion chair base kit to raise your Aeron chair to stool or drafting height Taller gas cylinder gives you a seat height range of 23" to 29" 20" Foot Ring, 5 Casters. If your Aeron chair was manufactured after 2012, this conversion kit for Aeron chairs will not work! This Aeron chair conversion kit is meant to be used in its entirety, and not mixed with existing parts ******VERY IMPORTANT WARNING****** IF YOUR EXISTING CHAIR THAT YOU WISH TO CONVERT TO A STOOL HAS A BACK TILTING FUNCTION, PLEASE BE SURE TO LOCK THE TILT. IF IT CANNOT BE LOCKED, DO NOT USE THIS PRODUCT. IT IS DANGEROUS TO RAISE THE HEIGHT OF A CHAIR TO A STOOL IF YOUR CHAIR BACK CAN FREELY ROCK BACKWARDS.*****