The Apeks RK3 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 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.