The progression tails are tuned to a neutral foot pressure. They have evolved out of the Shiv tail, our most popular of the 3 packs we've sold. The Progression tail is fairly thin giving it some extra speed and pumping efficiency over the Shiv. I've also pulled the tips in a bit more for sharper angles in turns.
 
Technical Specifications
Each model is available in 13.5"and 14.5"
13.5 suits lighter riders and more high-performance riding
14.5 suits heavier riders (80 kg plus) or for increased pumpability
