The Firestone 9000 is a sleeve style bag that is typically used on the rear of lighter vehicles that have a separate spring and shock. The Firestone 9000 replaced the Air Lift 58130 tapered sleeve bag. If your kit uses the Air Lift 58130 bags and you need a replacement, you will need to purchase the Air Lift Sleeve Bag Replacement Kit
which includes (2) Firestone 9000 bags and hardware. You should not
run a Firestone 9000 bag with the Air Lift 58130 bag. The bags are different lengths and mixing brands will cause your pressures to be different from side to side.