Gas props (also called gas struts, lift supports or gas springs) are sized by three things: how long they are when fully extended, how much force they push with, and what they connect to. Get the first two right and the lid will open smoothly and stay up.
1. Measure the extended length
Measure your old prop fully extended, from the center of one end socket to the center of the other. If the prop is still installed, open the lid all the way and measure it there. Write it down to the nearest tenth of an inch.
2. Note the compressed length
Compressed length is how short the prop gets when the lid is closed. You usually don't need to measure it: props with the same extended length for the same application share a compressed length. It matters when two props have the same extended length, since the one with the wrong compressed length can stop the lid from closing.
3. Read the force rating
The force is usually stamped or printed on the cylinder, often in newtons (for example 400N). Divide newtons by 4.448 to get pounds.
N = –
Match the original rating. A prop that is too strong makes the lid hard to close and puts stress on hinges and glass; too weak and the lid drifts down. If the old stamp is unreadable, note the part number printed on it, or send us a photo and we'll help.
4. Check the end fittings
Most camper shell doors and toolbox lids use 10 mm ball sockets. Heavier fiberglass tonneau covers such as Snuglid use a larger 13 mm fitting. Our props ship with ball mounts, so you can replace worn studs at the same time.
Find your prop
Enter your extended length (and force if you know it) to see the closest matches from our catalog.
Gas prop finder
Measure your old prop fully extended, center of socket to center of socket.
Install it rod-down
Mount gas props with the thin rod pointing down and the cylinder up whenever the geometry allows. That keeps the internal oil on the seal, which is what makes a prop last. See how to replace camper shell gas struts.
Common questions
Can I use a longer or shorter gas prop than the original?
It isn't recommended. A longer prop can stop the lid from closing or over-extend the hinges; a shorter one won't open the lid all the way. Stay within about a quarter inch of the original extended length.
Why does my lid only drop in cold weather?
Gas pressure falls as temperature drops, so a prop that is starting to wear shows it first on cold mornings. It is a sign the props are near the end of their life.
Should I replace both props at once?
Yes. Props wear at the same rate, and a new prop paired with a worn one makes the lid twist and wears the new one faster.
What does N mean on a gas prop?
N is newtons, the metric unit of force. Divide by 4.448 to convert to pounds: 400 N is about 90 lbs.