Device for adjusting seat height

A device for adjusting a seat height comprising:

• an outer tube adapted to be connected with a bicycle frame and including upper and lower ends spaced in a longitudinal direction;
• an inner tube received in the outer tube and being movable relative to the outer tube in the longitudinal direction, with the inner tube including an upper portion extending out of the upper end of the outer tube and adapted to be connected to a bicycle seat, with a connecting portion fixedly provided in the inner tube adjacent to the upper portion and provided with a screw hole extending therethrough in the longitudinal direction;
• a cylinder received in the inner tube and including first and second ends spaced in the longitudinal direction, with the first end being adjacent the lower end of the outer tube;
• and
• a piston rod received in the cylinder and being movable relative to the cylinder in the longitudinal direction, with one end of the piston rod extending out of the second end of the cylinder and having a screw portion thereon, wherein the screw portion is screwed in the screw hole of the connecting portion and has a head end which passes through the screw hole, wherein the inner tube is movable in the longitudinal direction relative to the piston rod by rotating the head end of the piston rod.