Monroe MA821 Max-Air Air Shock Absorber All Weather Fluid: Contains special modifiers to reduce friction and ensure smooth rod reaction Full Displaced Valving: Better valving range on both the compression and extension cycles of the unit for a smooth comfortable ride Sintered Iron Piston: Stronger than traditional metals, enhances durability for long service life Lubricated Air Sleeve: Reduces friction for longer service life Provides smoother operation during suspension movement 1/2" Piston Rod: Hardened and precision ground rod for consistent performance and long service life