Sivan Height Extenders (2&rdquo;) for Balance Ball Chairs; Set of 4 Add an additional 2" of height to your ball chair, Sold as a set of 4 Compatible with all Sivan 4 wheel balance ball chairs and most plastic chairs from other brands (adjustable and non-adjustable) Extends chair's suggested upper height limit to people 6' 1" tall Easy to install, no tools needed at all 100% Satisfaction Guarantee from SIVAN Health and Fitness