Sternum straps go across the shoulder straps of your BC, along the top of your chest. The sternum strap can be reattached in different positions to accommodate for varying chest sizes and BC fit. Oceanpro's sternum strap is unique, in that it has some elasticity. This enhances comfort, and the ability to fit varying chest widths and depths. The width of the sternum strap is also adjustable, to accommodate a vast range of users. The centre buckle makes for easy "on and off"" of the BC for your diving adventures. "