Mares has designed the Donut Buoyancy Bladder for Double Tanks to give technical divers the opportunity to use the mono SET harness they purchased previously. Any diver who has entered the XR world and decides to switch to the double tank, will only have to buy the bag. Its circular shape allows air to circulate easily and have the technical diver direct it towards the valves. According to your teaching guidelines, this bag offers you the option of placing the drain valve on the left or right.