These Pressure Relief Valves release air trapped in the lower legs of your RockShox fork, making your fork supple off the top with just a quick pressure release. Riders experiencing big changes in elevation on their riders will benefit the most from using these Pressure Relief Valves. The previous RockShox Pressure Relief Valve used a button style, while the new version unscrews via hand or 4mm Allen Wrench. If your fork uses the button style valves, these are not an upgrade, just a different design that accomplishes the same goal. Finger tight is perfect, no need to crank these down! Fork Compatibility List: Pike C1+ (2023+) Lyrik D1+ (2023+) ZEB A2+ (2023+) Boxxer D1+ (2024+)