This Replacement Gas Lift Cylinder fits 2 inch bases and 1.1 inch seat plates. If your chair is unable to adjust up and down, you may need to have the Gas Lift Cylinder replaced. All office chairs have an unique universal size and compatible with all office chairs sold in the USA/Canada. Outer cylinder has 2" in diameter, and the inner cylinder has 1.1" in diameter. Both cylinders' edge are slightly tapered for ease of installation. The cylinder has a minimum length is 11.4" which can be extendable to a maximum length of 16.3". The adjustable range of 5" in between will cover the height needed for most users.