The cylinder of a universal seamless gas cylinder is cylindrical, with a convex, concave, or H-shaped bottom at one end and a spherical shoulder with a neck at the other end. On the top of the bottle neck is a bottle mouth with a conical pattern, which is used to assemble the bottle valve.

In order to make the cylinder with convex bottom stand upright on the ground, the lower part of the cylinder with a volume equal to or greater than 12 liters is usually equipped with a cylindrical or quadrangular base, which is sheathed on the cylinder under the red hot state. The distance between the grounding plane and the highest point of the convex surface of the cylinder bottom should not be less than 10 mm according to the standard requirements.

On the cylinder containing permanent gas and liquefied gas with a volume equal to or greater than 5 liters, a collar with an outer screw is sheathed on the outside of the bottleneck to install a cap or protective cover for protecting the cylinder valve.

Bottle caps are divided into fixed type and removable type. The purpose of the fixed cylinder cap is to prevent the cylinder valve from being damaged during transportation and use. In addition to the function of fixed bottle cap, the detachable bottle cap can also prevent dust, dirt, grease and water from falling onto the bottle valve. In order to avoid pressure in the detachable cap when the cylinder valve is not tight, the cap cylinder is provided with two opposite holes, which can also be used for hanging lead seals during long-distance transportation.