Flying Diamonds of California Skindog Twin Fins This is Ben’s performance Twin Fin designed for all styles of twin fin boards. These fin sets give you the smooth, drivey feeling of a traditional keel, with a blend of the newer upright performance style fin. The outcome of this is a power-based performance twin fin. Perfect for all twin fin designs and versatile in all conditions. These fins are hand-foiled offering a stiff base with subtle responsive tip flex, amazing aesthetics, and proven durability.