Seatposts are manufactured in a number of different materials, with aluminum, titanium and carbon fibre seatposts being the three main types. Aluminium seatposts, above - do a good job, however carbon seatposts provide greater performance and dampening from vibrations, whilst being lighter.
Alloy seatposts are better for riders who ride demanding and tough terrain - aluminium seatposts are tougher than their carbon fibre counterparts so are more suited to mountain bikes, including downhill mountain bikes.