US Patent 10202158 Adjustable seat tube structure and bicycle

An adjustable seat tube structure which is for adjusting a height of a saddle for a bicycle includes a lower tube, an upper tube and a piston set. The lower tube includes a top end. The upper tube is disposed at the lower tube and is limitedly moved relative to the lower tube. The upper tube is linked with the saddle and includes an upper end, an inner space, and a lower end. The upper end is protruded out of the top end, and the inner space is for receiving a gas. The lower end is corresponded to the upper end. The piston set includes a piston, a valve and a rod. The piston is disposed inside the inner space, and the lower end is moved relative to the piston. The valve is disposed inside the piston and the rod is connected to the piston.