*Does NOT Work for Walker Evans Reservoirs* Includes 4 Reservoir Caps Made for Fox Reservoirs 2.5" in diameter Our MTS Reservoir caps allow for easy and regular nitrogen service, and allow you to exceed 200 PSI. Easy and regular checks: With our easy-to-fill Schrader Valve, your nitrogen can be checked and filled faster and easier than typical pellet caps. Nitrogen should be checked at least twice a season, as shocks typically lose 30 PSI every 6 months. Going below 150 PSI can cause cavitation in your shocks, which can cause unnecessary heat, premature wear, and a decrease in handling. Higher PSI Capacity - MTS Reservoir caps allow for up to 300 PSI of nitrogen, while OEM pellet cap styles will not allow you to exceed 200 psi, and for larger vehicles and more aggressive drivers, this extra nitrogen will prevent cavitation and added bottom-out resistance.