The Backplate, a plate, generally made out of chrome steel, often aluminium or carbon fibre composite, which can be held from the diver's back through the harness, and to which the diver's Major cylinder or cylinders are connected. Other types of BCD exist which a lot more resemble backplate and https://click4r.com/posts/g/20919287/scuba-scooter-sand-305-rlarand-305