Gas Strut End Fittings and Sizing: How to Measure Before You Order

A gas strut only works if three things match: the length, the force, and the ends. Get one of them wrong and the lid either won’t lift, won’t stay up, or won’t close cleanly. This guide covers what to measure, how the common end fittings differ, and how to decide between regassing and replacing.

The four things to measure

Work from the strut you’re replacing, or from the geometry of the lid if you’re building something new.

• Extended length — from the centre of one mounting point to the centre of the other, with the strut fully out. This is usually the first figure listed for a strut.
• Compressed length — the same measurement with the strut fully closed. Extended length minus compressed length gives the stroke, which is how far the lid can travel.
• End fitting type and size — ball socket, clevis, eyelet or threaded stud, and the size each end accepts.
• Force rating in Newtons (N) — usually marked on the strut body. If the marking has worn off, work from the application and the weight of the lid instead.

Measure with the strut off the vehicle or lid, so it sits at its natural extension and you’re not measuring against a load. Once you have those four figures, match them against our gas struts.

Matching the end fitting to the bracket

Most ordering mistakes happen at the ends, not the middle. Each fitting type has its own things to check.

Ball socket. Clips onto a ball stud, and is held by a spring clip or a retaining pin depending on the design. Check the ball size the socket accepts and how it is retained. Sockets wear over time and can pop off under load, so if the socket is loose on the ball, replace the end or the whole strut.

Clevis and clevis pin. A clevis is a forked end that straddles a bracket, with a clevis pin through it to hold it in place, usually retained by a split pin or clip. It’s common where the strut needs to pivot as the lid moves. Check the pin diameter, the gap between the fork legs, and the hole size in the bracket.

Eyelet. A plain ring that takes a bolt or pin through it. Check the inside diameter of the eye and the thickness it has to clear.

Threaded stud. Screws into a tapped bracket or a threaded ball stud. Check the thread size and pitch, and how much thread engagement you get once it’s wound in.

If one end is worn and the other is sound, it’s still usually simpler to replace the complete strut than to chase individual ends — that way length, force and fittings stay matched.

Why the force rating isn’t a guess

Force is the push the strut provides, and it only works in your favour if the mounting geometry suits it. Two things drive the number: how heavy the lid or hatch is, and where the strut is mounted relative to the hinge and the lid’s centre of mass. Moving a mounting point changes how much of the strut’s force reaches the lid, so the same strut can feel too strong in one installation and too weak in another.

That’s what a gas strut calculator is for. It takes the lid weight, the hinge position and the mounting points, and works out the force you need. Have those figures ready before you use one, and treat the result as a starting point rather than the whole answer — the strut also has to physically fit, so extended length, compressed length and end fittings have to work at the same time.

Replacing like for like on a standard toolbox, canopy or camper lid is usually the simplest path: match the original force and dimensions. If the lid itself has changed — heavier material, extra lining, a spare wheel mounted on it — the original force may no longer suit, and it’s worth recalculating rather than ordering the same number again.

Regas or replace?

A strut that has lost force but still has a clean rod and sound ends can sometimes be regassed. The condition of the rod is the deciding factor: a scored or corroded rod usually points to a worn seal, and regassing won’t fix that. Worn ball sockets or oval clevis pin holes need new ends regardless.

For most toolbox, canopy, caravan and camper applications, a replacement strut is the quicker and more predictable option, because it restores the original force and both end fittings in one step.

Symptoms are a useful guide. A lid that won’t stay up on its own has usually lost force. A lid that drops suddenly, or that needs a firm push to start moving, often points to a fitting or alignment problem as well as force loss.

What to have on hand before you order

• Extended length and compressed length
• Force in Newtons
• End fitting type and size at each end
• The application, and what the strut is holding up

If any of those are unknown, a photo of the strut with a tape measure alongside it, plus a photo of the mounting brackets, is usually enough for us to work from. Getting the measurements right the first time saves a return and a second lot of freight, particularly on lids that are awkward to hold open while you swap a strut over.