FCS Al Merrick Tri-Quad Surfboard Fins Material: Performance Core Compatibility: FCS Fin II System Base Length: [medium] (front, rear) 4.55, 3.83in, [large] (front, rear) 4.61, 4.09in Depth: [medium] (front, rear) 4.52, 4.7in, [large] (front, rear) 4.7, 4.26in Area: [medium] (front, rear) 14.89, 11.08in, [large] (front, rear) 15.63, 12.63in