The Apeks RK3 Hard is the latest addition to the RK3 series. Made with a higher density (HD) than the standard RK3, the fin is stiffer and has negative buoyancy, making it ideal for wetsuit diving. The RK3 HD is available in three sizes : small, medium, and large. The RK3 HD fins are available in three sizes: small, medium, and large. the RK3 HD fins are misleading because they do not indicate shoe size. For example, are you diving in a warm environment with wetsuit boots or walking on a pebbly beach with a dry suit and stiff dry boots? Both footwear are size 9, but occupy different space in the foot pocket of the fin.
