Weighting must be sufficient to allow the diver to stay at the shallowest stop with empty cylinders, and available buoyancy volume must allow the BCD to support the full cylinders. The absolute minimum volume for the BCD is enough to support the total mass of breathing gas in all the cylinders the diver will carry, plus lost volume due to suit compression at depth. This will be enough only if the diver carries no excess weight. It is easier to allow for a slight weight excess and use a slightly larger volume BCD, but if taken to excess this will make buoyancy control more difficult and labour-intensive, and will use more gas, particularly during ascent when it is most critical. A BCD designed for recreational diving or for a small person may not have sufficient volume for technical diving.