A gas strut comprises of a piston rod which slides in and out of a pressurised sealed tube. The rod has a piston riveted to one end which prevents it from being forced out of the tube when pressurised. The force of the gas strut is provided by the gas pressure acting on the cross sectional area of the rod. The higher the gas pressure, the higher the force of the strut. The piston has a metering orifice which allows the gas to pass from one side of the piston to the other. By altering the size of the orifice, the rate of extension can be varied.

Gas struts have numerous uses throughout industry. They are most commonly used as a counterbalance for lifting lids, hatches or doors. They can also be used for the direct support of sliding columns, tensioning devices and dampers.
Typical applications include:

• Car Tailgates
• Skylights
• Sunbeds
• Boat access hatches
• Coach luggage doors
• Electrical Contol Cabinets
• Machine guards
• Office Furniture
• Vending Kiosks

Figure 1 below shows how the force of a gas strut increases as the gas strut is compressed. The force increase can be expressed as a ration (Rc) or the spring rate, values of which are given in figure 2.