This swallow tail single fin has a flat vee with a double concave through the tail. This board is meant for barrels or bigger waves. Suggested fin size is 7" - 8". This pin tail single fin has a flat vee with a double concave through the tail. This board is meant for barrels or bigger waves. Suggested fin size is 7" - 8". This double wing pin tail single fin has a flat vee with a double concave through the tail. This board is meant for barrels or bigger waves. Suggested fin size is 7" - 8".