 One of the advantages of the sidemount system is the easy access to cylinder valves, and the protected position they occupy in comparison with most back mount systems, where the valves are relatively vulnerable to bumping against an overhead and being "rolled off" (closed by rubbing against the overhead).The standard arrangement for sidemount is that all cylinders are independent, and each is provided with a single demand valve, an SPG, and on one or two, a low pressure inflator hose for buoyancy compensator and, if used, the drysuit.This implies that if gas is shared in an emergency, the recipient will be breathing from a different cylinder to the donor, unlike the more usual arrangement with backmount, where both divers breathe off the same set.