backplate and wing includes: Stage or decompression cylinders. "Tow behind" diver propulsion vehicles, which use a tow-cord, attaching to the crotch strap D-ring of the harness. Pockets. Cutting tool sheath. Lights/torches, and light/torch battery canisters. Much of this equipment is difficult or impossible to attach to other styles of BCD. Images Comparison with alternative equipment The predominant type of BCD currently used in recreational diving is the jacket style BCD. The backplate and wing differs from the jacket style primarily in the way that the functions required of a BCD (attachment to diver, buoyancy control and attachment to cylinder(s)) are performed by distinct components, rather than a single unit. The most significant effects of this division are shifting the buoyancy bladder from the diver's chest to their back and the modularity of the system, allowing buoyancy cells, harnesses, and plates to be interchanged as needed. The buoyancy of a backplate is often significantly negative, especially when the plate is made from stainless steel, and so can replace some of the weight that would otherwise be worn on a weightbelt. Ancillary features that would often be present in jacket BCDs, such as pockets or weight integration, are not found in the core system of a backplate and wing, but can be added as additional components if desired. Other types of BCD exist which more resemble backplate and wing BCD. Back-inflation BCDs are similar in construction to jacket BCDs, except for where the buoyancy cell is. In a back-inflation BCD, as with a backplate and wing, the cell is behind the diver's back, and is of similar shape to a wing, but a back-inflation BCD usually does not have the modularity of a backplate and wing, although some models let buoyancy cells be substituted. Softpack BCDs are another style closer still to backplate and wing BCDs. Softpacks, like backplates, are designed to be modular, and are often marketed towards technical divers. A softpack consists of a padded semi-rigid section that serves that same purpose as a backplate, and uses a harness that is either replaceable, like a backplate harness, or permanently fixed. Softpacks may be used with the same models of wings that are used with backplates. The primary differences between these and backplates are the lack of a rigid plate and possible non-separability of the softpack and harness. The relatively low density of the softpack usually necessitates more ballast weight. A