The Original K2.1, Kelly Slater designed the fin for maneuverability and speed off the top. The side and center fins have different templates, foils and flex patterns. The larger, more upright side fins have greater flex for tighter and faster turns. The smaller, stiffer center fin adds control. Base:4 3/8" (110mm), Depth: 4 1/4" (115 mm), Area: 15.2 sq in (9824 mm2), Sweep: 32 degrees.