Surfboard Fins K2.1 - Dual Tab Thruster - CARBON BASEK2. 1 style surfboard fins in Dual Tab Thruster with Performance HexCore + CARBON base K2. 1 fins are renowned for excellent performance in hollow beach break style waves. A more 'up and down' fin, they emphasise pivot and are suited toward tight pocket surfing base: 110mm depth: 115mm also available as a Quad set Carbon base and Performance HexCore inlay for extra responsive power. For those who surf critical, these advanced carbon fins provide a