Here you can see a cutaway of a Bilstein 5150 Series remote-reservoir shock. This particular unit has a fixed-reservoir (or piggyback) design and was the first production monotube high gas pressure, fixed CrossFlow reservoir shock designed specifically for lifted and custom applications. The CrossFlow fixed-reservoir design expands oil capacity for enhanced cooling and it also allows for increased rod travel. This high-pressure (360 psi) nitrogen shock's reservoir features a "floating" dividing piston that eliminates the possibility of oil foaming and performance loss from shock fade. The monotube design provides superior tube strength while maximizing heat dissipation and shock life. It has a 46mm working piston and self-adjusting deflective disc valving (visible in the monotube), which allows for maximum vehicle body control and superior performance. The 5150 can be valved for single- or multiple-shock applications; it is available in 6.5 to 14 inches of travel and has a platinum powdercoat finish.