Superior Performance from Advanced Technology In more than 30 years since Bilstein introduced the world's first production monotube gas pressure shock absorber, no other shock manufacturer has been able to equal its performance. The Bilstein name today graces not only shock absorbers, but also single and dual tube Macpherson strut style suspensions. Bilstein's monotube design exposes the shock body to maximum air flow, lowering the operating temperature of the internal components and fluid, extending life. The nitrogen gas is separated from the superior grade oil by a specially designed, close tolerance, floating piston. This design maintains constant pressure against the hydraulic fluid, absolutely eliminating fluid aeration and performance loss that is common to conventional twin tube design shocks.