Oajen gas cylinder for office chair 5" stroke, fits most office chairs with 2" diameter black pipe or chair base center hole 5" stroke gas cylinder for office chair Fits most chair base with 2" opening in the base. Exceeds BIFMA quality. Overall length extended is 16-3/4". Made in Taiwan. if you want heavy duty gas cylinder for large person http://www.amazon.com/gp/product/B00DGXHA4W For 3" stroke, http://www.amazon.com/gp/product/B007ZT4A7S