RS5000X Gas Shock, The core of this new,innovative shock from Rancho is the unique,patented rebound valving system,an advanced compression phase of the shock absorber. This proprietary process developed by the ride engineers at Rancho will elevate the overall handling,performance of your vehicle on,off-road. Each RS5000X shock is gas pressurized to 150 PSI.* The twin tube, gas pressurized shock has a variety of advantages including minimizing air-to-oil mixture that can cause foaming,shock fade. Gas pressurization also provides a mild boost of spring rate to the vehicle. The RS5000X series features a 2-1/4-inch diameter shock body. A larger shock body allows for increased fluid capacity to operate cooler,to increase vehicle control,performance at varying speeds,terrains. The RS5000X series combines a larger shock body with all-weather fluid, allowing the shock to withstand internal temperatures between -40,248 degrees Fahrenheit. The Rancho RS5000X series design includes patented progressive rebound,compression discs. At lower speeds or in the earlier stages of the shock's travel, an eccentric disc in the valve shim stacks will engage the valving at lower frequencies, helping to control the energy of motion as the cycle of the shock increases or decreases in its action. When hitting a pothole, off-road trail obstacle or similar activity, Rancho's Progressive Engagement Valving allows for early flow of fluid, helping to reduce harsh initial impacts,to control the flow of fluid in a progressive, gradual manner through the valving. During on- or off-road driving activities like washboarding or when travelling a rough fire road, the early flow of fluid helps to minimize a "rough" ride as the piston movement is able to glide through the initial travel motion of the shock with minimal ground impact or force. If needed, the Progressive Engagement Valving will further engage to maintain control,stability.