Length 550mm. Stroke 240mm. Force 300N. Shaft 8mm 18mm cylinder. Various end fittings available. ***Gas stays carry 2yr warranty*** Length of gas stay = H measurement (half the depth of the door from hinge point) + 20% L= mounting distance from hinge (Guide: 405 long = 150mm, 500 long = 200mm, 605 long = 250mm, 700 long = 290mm, H= half the depth of the door from hinge point. G= weight of the door in Newtons (1kg = 10 N) Force = G x H ÷ L, + 30%, divided by number of stays being used = Newton force..