All BCD's

A BCD is a fundamental part of the scuba (Self Contained Underwater Breathing Apparatus) unit.  It functions as a central device that the diver wears to hold the tank, it should comfortably fit the diver with padding where necessary.  The BCD often has multiple D-Rings fitted to it or can be added, to allow the attachment of accessories like a reel, SMB, camera, pointer, etc.  Mounting the tank on your back (Back Mount) or your side (Sidemount) is now both common in diving across the world.  Whatever your choice, make sure it fits correctly and you are trained (if needed) how to use it safely. 

 Remember a BCD is a life-saving device, as it allows you to float positively buoyant on the surface before and after dives; so always remember to have it serviced regularly just like your regulator.  This will help avoid leaks and failures, which could become life-threatening.