Abstract: A gas spring comprising a cylindrical body in which a main piston is slidable and carries a piston rod extending in sealed manner outwardly of the cylinder. The main piston includes a bore connecting with a labyrinthine passageway. The interior of the cylinder contains a fluid comprising gas under pressure and (optionally) some oil. The gas urges the piston rod outwardly of the cylinder. During the corresponding travel of the piston, the fluid transfers from one side of the piston to the other in a controlled manner through the bore and the passageway to allow relatively rapid travel. However, when the main piston comes into contact with a second piston, freely slidable on the piston rod and biassed towards the main piston by a compression spring, this contact closes off the end of the fluid passageway, and fluid can now only transfer through the main piston by passing through a narrow radial channel, thus reducing the speed of outward travel of the piston rod.