The M-3 Mainsail design is built primarily out of Contender 3.8 PK in the body and features a large radial clew box to keep the lower sections very straight in the back and a nice radial head for ultimate smoothness and durability. The sail is fast throughout the wind range and requires less rig tuning to keep it in it's 'sweet' spot which allows you to keep your head of the boat more to help you win.