**Shock Therapy billet reservoir caps are sold in PAIRS. If you need caps for a full set of Shocks, please make sure that your order quantity is "2"** The Shock Therapy Billet Aluminum reservoir caps are available for any Fox shock that utilizes a 2.5" reservoir body! Our Caps are designed and manufactured in the USA. We start with a block of Aircraft grade 6061 T6 billet aluminum that is CNC machined then hard coat Anodized. Integrated cooling slots/fins increase the surface area to help with cooling during heavy use. The addition of a high-pressure nitrogen purge/fill valve increases the serviceability of the shock system since you will not need any proprietary equipment to maintain the nitrogen charge. Our reservoir cap is engineered to increase the nitrogen volume in the shock system which will result in a more consistent feel throughout the full range of shock travel.