Seat Posts & Parts
A bicycle seatpost or seatpin is a tube that extends upwards from the bicycle frame to the saddle. The amount that it extends out of the frame can usually be adjusted, and there is a mark that indicates the maximum extension. Seatposts can be made of steel, aluminum, titanium, carbon fiber, or aluminum wrapped in carbon fiber.
Seatposts generally clamp onto saddle rails, while other seatposts slide into a separate clamp that then clamps the saddle rails.
!