The BiAir® membrane air spring insulator is made of turned or cast aluminium. The air space is enclosed by a thin-walled flexible and pressure-resistant rolling membrane. A piston sits on top of the membrane and is pressed into the air space.This design allows a highly-effective insulation against vibration. In order to simultaneously achieve a high degree of damping, the air space within the insulator is divided into two chambers connected with an air tube (load/damping volume). An adjustable throttle valve is used to set the flow cross section to the desired damping effect from the outside. The friction in the air flow generated by the throttle valve can create a damping effect of up to 15%. Damage to the rolling membrane due to overpressure is virtually excluded through the use of additional safety valves or a mechanical piston stroke limit.