These springs are sometimes referred as tension or pull gas springs. A gas traction spring functions the opposite way of a gas push spring. In neutral position the piston rod is inside of the cylinder.
These springs are built on a two cylinder principle. Gas is only at one side of the piston. This gas is compressible.
With sufficient external force, by pulling the piston rod out of the cylinder, the gas traction spring will compress the gas into the outer cylinder. The gas in the outer cylinder will reach consequently a higher compression. When the tension force is reduced, this gas will return the piston into its original position.
A gas traction spring can only be used with the rod pointing up.