Abstract: 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.

Abstract: 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.

Abstract: An electrically controllable seat post is provided. The electrically controllable seat post includes a retractable rod and a switch actuator. The retractable rod includes a switch. The switch actuator is corresponding to the switch and includes a pushing member, an electromagnetic coil and a controller. The pushing member is assembled in the switch actuator, wherein the pushing member is controlled to move to open or close the switch. The electromagnetic coil generates a magnetic force by injecting a current therethrough, wherein the pushing member is moved by the magnetic force. The controller controls the switch actuator.