An adjustable height seat post for bicycles that comprises an inner tube slidably contained within an outer tube which supports a bicycle seat. The outer tube clamps into a bicycle frame and contains a spring which acts to force the inner tube upward. The inner tube is allowed longitudinal movement within the fixed outer tube via a locking mechanism that forces ball bearings into pockets or channels on the inner tube. The locking mechanism can be remotely activated with a handlebar mounted lever or manually with a seat post mounted lever.