i know they took the place of the light speeds and they have a new nock design and something else maybe its a new insert design i cant remember but they are about 6fps faster than the lightspeeds of the same weight so i am told. i know most of the guys at my local pro shop are shooting them this year. one of them was shooting the maximas and he said the flatlines shot more true than the maximas and they shot better through paper... well at least they did through his bow.