Air FX Front Air Ride cartridge pair for Harley-Davidson applications Air FX Front Air Ride Kits make it easy to up-grade your factory internal fork assemblies. These replacement style cartridges are a perfect fit. Each cartridge has 2 chambers for lift, and 2 for rebound in axial alignment. This allows us to increase piston surface area, thus reducing air pressure required to lift. To dampen compression during hard braking we have add a booster spring. The result is a much smoother, and consistent ride and increased handling. Each kit is specifically designed to fit your bike without modification and exceeds all manufacture specifications.