The RK3 HD fin is the latest in the RK3 range. It is made from a higher density material than the standard RK3, which makes the fin stiffer and heavier and is therefore the ideal fin for dry suit diving. The new, heavier compound makes it negatively buoyant and produces a stiffer blade, providing additional power in heavy currents or surf. Based on one of the first vented rubber fins sold in North America and popular among military and professional divers Compact, and ultra-rugged for use in harsh environments Improved foot pocket with spring straps for ease of use with cold hands or thick gloves The design has been the standard gear issue fin for military, special ops, coast guard and public safety divers for decades Short wide blade provides maximum forward thrust while maintaining great maneuverability Vented blade design reduces resistance on the upstroke and enhances thrust on the downstroke The vents also eliminate vortexes that can occur along the back of the blade much in the same way split fins eliminate the vortex The blade material designed to hold up in the toughest environments, temperatures and abuse Two large grommet holes designed to fit most carabineers for easy storage of the fins Spring straps as standard Custom designed buckle holds spring straps in optimum position 3 sizes available: Medium (7-9), Large (9-11) & Super (12+) Colors: RK3 HD - black, grey