Gas springs can be defined as hydro-pneumatic, energy storage elements. Nitrogen gas and oil are utilized for providing compressible and damping (motion control) mediums. Gas springs can be configured to meet a wide range of requirements. The main components of a gas spring are a cylinder, a piston rod with piston head, a seal and a guide. The cylinder is filled with compressed nitrogen gas, which applies equal pressure on both sides of the piston. The surface of the piston rod side of the piston is smaller than on the opposing side, producing a pushing force. Used in doors, bonnets, chairs, trunks etc.