Firestone replacement air bags are intended to replace an old, worn out, or defective air bag from your original firestone air bag kit. This spring is a convoluted style bag meant to replace a Ride Rite kit.
This air spring is the same as 6397 but with 1/8 NPT 5/8"- 18 x 1.75 Combo Stud
Long Part #: W21-760-6410, W217606410