The Apeks RK3 HD is the latest model in the RK3 range. It is made from a higher density (HD) than the standard RK3, which makes the fin stiffer and with negative buoyancy, ideal for wetsuit diving. The Apeks RK3 HD is a rugged thermoplastic rubber fin featuring an over-sized foot pocket to accommodate drysuit boots and a spring strap for easy donning and doffing. The RK3 HD is available in four sizes: Small, Medium, Large and Super. We didn't give the RK3 HD fin a shoe size range as this can be very misleading. The environment that an RK3 HD is used in will tend to dictate the size of fin that you need, for example do you dive in a warm environment wearing wetsuit boots, or are you walking across pebbled beaches and wearing a drysuit and rigid dry boots? Both forms of footwear may be a size 9, but will take up different amounts of space in the fin foot pocket.