Gas cylinder

An air pressure rod comprises an empty tubular outer cylinder that extends vertically, an empty tubular inner cylinder that is coaxially consolidated in the outer cylinder and internally defined as an air chamber, a piston that can move up and down an airtight plug installed in the inner cylinder, a piston rod extending downward from the piston out of the outer cylinder, and a control device that is airtight installed in the upper end of the inner cylinder; The inner cylinder has a cylinder wall made of hard plastic material and the outer peripheral surface is fixed on the inner peripheral surface of the outer cylinder, and a flow channel extending upward from the bottom surface of the cylinder wall and connecting with the upper end of the gas chamber with a top end of the flow channel. Often used for office tables and chairs.