Monroe 33121 Monro-Matic Plus Shock Absorber All Weather Fluid: Contains special modifiers to reduce friction and ensure smooth rod reaction 1-3/16" Bore: Larger bore than most shocks to provide more efficient and consistent control Nitrogen Gas Charged: For improved ride and handling, helps maintain tire to road contact by reducing aeration 1/2" Diameter Piston Rod: Nitrocarburized rod for long service life Special Seal: "Self-lubricating" fluid seal designed to retain gas without excessive wear or friction