This is Kelly Slater's raked template designed to maximize hold and generate drive, and is the complimentary opposite to the KS1 pivot template. Kelly prefers to ride size Large in smaller waves, and Medium in bigger waves.
Rake refers to how far back the tip of the fin reaches beyond the base of the fin - this design translates into more drive and wider, more drawn-out turns.
Single Tab variants are compatible with Futures' fin system.