A gas spring consists of a cylinder with a piston, which compresses gas inside the cylinder, creating a springy effect. A valve in the piston dampens the movement. A gas spring can be used, for example, for a height-adjustable office chair. If you want to adjust the seat height of an office chair, the lower leg length is the determining factor. When adjusting the seat height, the feet should be able to remain flat on the floor, while also preventing pressure from building up on the underside of the thighs. The feet, thighs, and seat should support and distribute the body weight. The height of the chair's seat then depends partly on the chair's forward tilt.