All Weather Fluid: Contains special modifiers to reduce friction and ensure smooth rod reactionFull Displaced Valving: Better valving range on both the compression and extension cycles of the unit for a smooth comfortable rideSintered Iron Piston: Stronger than traditional metals, enhances durability for long service lifeLubricated Air Sleeve: Reduces friction for longer service life Provides smoother operation during suspension movement1/2" Piston Rod: Hardened and precision ground rod for consistent performance and long service lifeThe Max-Air shock absorber is ideal for vehicles that haul heavy loads or tow trailers. Designed to maintain level vehicle height, they can be inflated or deflated as needed...from 20 psi to 150 psi with the vehicle loaded. A pair of Max-Air shock absorbers can maintain ride height when up to 1,200 lbs of additional weight is loaded.