Quote: (Originally Posted by
reinoud)
The only people I see in DIR with twin 18 or 20 litres are the exploration cave divers with rebreathers...
Double 18s are useful in cave even without an RB80 between them. It's a set up that can be used from C1 upwards. D18s are very similar to the D104s/120s used in America. I think the main reason we don't see more D18s in cave diving in Europe is that D12s are the standard ocean diving cylinder and most people have multiple sets of D12s. Adding an(other) AL80 is an easy alternative with D12s for most dives.
Cylinders of this size also have their place for ocean diving. At the point when you'd need a bottom stage plus 3 deco gasses with D12s then larger backgas cylinders start to make sense.
David