Product Details The all newChinook Sailing 1-Bolt Pro Flex Mast Base US Base Cupfeatures all of the advantages of a tendon base with the added features of a mechanical base. Same shock absorption as standard Tendon bases for less stress on board, & sailor. Uses standard Chinook Tendon for easy serviceability. Free moving Mechanical hinge provides ease of attachment for larger or wider Foil boards, Formula, & Long boards etc. Small boards less likely to flip over during waterstarts in high wind & wave conditions. Mechanical hinge eliminates an estimated 75-80% of fatigue which occurs due to constant bending of the Tendon. Available in 2 Bolt andEuro-Pin EXversions