Gas springs provide controlled motion and speed for elements, such as lids and doors, that open and close. The absorption or damping action for gas springs can be compression or extension. In a compression gas spring the shock absorption or dampening occurs in the compression direction. In an extension gas spring the shock absorption or dampening occurs in the extension direction. Important physical specifications for gas springs include the cylinder diameter or maximum width, the rod diameter, mounting, and body material. The cylinder diameter or maximum width refers to the desired diameter of housing cylinder. The rod diameter refers to the desired diameter of extending rod. Choices for body materials include aluminum, steel, stainless steel, and thermoplastic. Common features for gas springs include adjustable configuration, reducible, locking, and valve. An adjustable configuration allows the user to fine tune desired damping, either continuously or at discrete settings. A reducible gas spring has an adjustment style for gas shocks in which gas is let out to permanently reduce force capacity.