This is the C4 Red Falcon HyperTech Carbon Fiber PAIR Replacement Blades (Blades Only) Features: One pair of blades with no footpockets Hyper Tech high-tensile carbon fiber exclusive to C4 in the fin industry TR-50 Big Square" pre-preg carbon fiber construction Much lower crisscrossing of the strands for high elastic return 34" length x 8.15" width (865x207mm) High gloss finish DPC - Double Parabolic Curve Foot pockets and mounting kit sold separately. 25/Soft - This stiffness is suited for divers who weigh -175lbs, diving between 20-80&'; with a mix of surface swimming and deeper diving/spearfishing. 30/Medium - This all around medium stiffness is intended for divers who weight 175-210lbs, engage in surface as well as a mix of shallow and deep diving to 30 meters (100&';). 40/Hard - This stiffer blade is generally indicated for bigger divers weighing over 200lbs or with a strong preference for deep spearfishing to a depth of 40 meters (130&';). The stiffness of the blade renders this blade stiffness choice well suited to overcoming added negativity at depth and rapid acceleration requiring more power and energy from the divers&'; legs. The 40 stiffness are not recommended for beginners and lighter divers as they can contribute to ankle strain and reduced bottom times. "