The tendon joint is stiffer than the flex-joint, this results in less deflection off of center and more direct energy transfer from the rig to the board. Of the three joints it is the lowest so the gap between sail and board is at a minimum. It is preferred by professionals. The tendon stiffness occasionally flips short boards after a fall requiring you to right it before waterstarting. The base can be loosened for quick mast track adjustments even in the water. 1-bolt design offers alittle more fore/aft adjustment in the mast track than the 2-bolt design.