The Al80 in cold water is a pernicious tank. If you compare it with steel tanks with equal empty gross weight, the Al80 is about 5 lbs more positive, meaning that you have to carry five pounds more ballast to dive the Al80. And other tanks, with equal weight and better buoyancy, have more gas. Al80's are plentiful and cheap, but that's about all that you can say about them, and they are not good cold water tanks. On the other hand, technical divers use them as stages, so you CAN resell them. A steel tank will give you more gas, less ballast, and the same or slightly more total weight.