What Is a Gas Strut and How Does It Work? (UK Guide)

A gas strut (also called a gas spring or lift support) is a sealed steel cylinder filled with pressurised nitrogen gas and a small amount of oil. The gas pushes a piston rod outwards with a steady force, measured in Newtons (N), which lifts a lid, door, bed base or car boot and holds it open. When you push it closed, the rod moves back into the cylinder and compresses the gas, ready to lift again next time.

Gas strut in one sentence

A gas strut is a compact, maintenance-free spring that uses compressed nitrogen instead of a coiled metal spring to give a smooth, controlled lift.

How does a gas strut work?

1. Pressurised nitrogen. The cylinder is filled with nitrogen at high pressure. Nitrogen is used because it is inert, so it does not react with the seals or the oil.
2. Piston and rod. A piston attached to the rod sits inside the cylinder. The gas pressure acts on the area of the rod, pushing it out. This is what creates the lifting force.
3. Small hole in the piston. As the rod moves, gas passes through a tiny orifice in the piston. This controls the speed, so the strut extends smoothly rather than snapping open.
4. Oil damping at the end. A little oil in the cylinder slows the rod in the last part of its stroke, giving a soft stop when the lid is fully open.
5. Seals and guide. A precision seal keeps the gas in. When the seal wears after years of use, the gas slowly escapes and the strut stops holding the weight — this is the most common reason a gas strut needs replacing.

What do the numbers on a gas strut mean?

• Force (N): the push the strut gives, e.g. 100N, 600N, 1200N. Roughly, 10N lifts about 1kg at the strut, but leverage changes the real figure, so always match the force printed on your old strut or use our gas strut force calculator.
• Extended length: measured centre to centre of the end fittings when fully open.
• Stroke: how far the rod travels between fully open and fully closed.
• End fittings: how the strut connects — usually a 10mm ball socket, an eyelet (eye end) or a threaded M6/M8 stud. See our end fittings compatibility guide.

Where are gas struts used?

• Ottoman and storage beds — 600N to 1200N struts lift the mattress platform.
• Car boots, tailgates and bonnets.
• Kitchen wall cabinets and toolbox or ottoman lids — light 60N to 150N struts.
• Office chairs — a gas lift cylinder is a gas strut adapted for height adjustment.
• Trailers, machine guards, hatches and caravan lockers — see heavy duty gas struts.

Gas strut vs gas spring vs hydraulic damper

In the UK, gas strut, gas spring and gas lift usually mean the same part. A hydraulic gate closer is different: it uses oil to slow a closing movement rather than gas to lift. Read more in gas strut vs gas spring.

Signs your gas strut has failed

• The lid, bed or boot drops or will not stay open.
• You have to push it the last few centimetres.
• Oil marks on the rod or a hissing sound.
• One strut is weaker than the other — always replace gas struts in pairs.

How to choose a replacement gas strut

1. Read the force (N) and part number printed on the old strut.
2. Measure the extended length centre to centre and the stroke.
3. Check the end fittings at both ends.
4. Fit the strut rod-down where possible so the seal stays lubricated.

Not sure? Send us a photo of your old strut and we will confirm the exact match before you order. Orders placed Monday to Sunday before 16:00 are dispatched the same day, via Royal Mail, Yodel, UPS or DPD.

Further reading

• Gas strut vs gas spring: how to tell the difference
• Gas strut replacement parts: sizing, fitting and troubleshooting
• How to measure your car bonnet or tailgate gas strut
• BMW boot gas strut replacement guide
• Cabinet lift hardware: gas strut kits vs branded systems
• Clevis fork end fittings explained (DIN 71752)
• DIN 934, 985 and 71802 standards explained

Frequently asked questions

How long do gas struts last?

Typically 5 to 10 years or tens of thousands of cycles, depending on load, temperature and how often they are used.

Can a gas strut be re-gassed?

No. Gas struts are sealed units and are not designed to be refilled — replace them instead.

Can I use a stronger gas strut?

Slightly stronger (about 10–20%) is usually fine for a heavier lid, but too strong makes it hard to close and can damage hinges or mounting points.

Which way up should a gas strut be fitted?

Rod pointing down, where the mounting allows. This keeps the oil on the seal and makes the strut last longer.