In reply to NickJH: I've got one however I got it to replace a Black Ice (size 2). I've found it great and regularly use it for multi-day hillwalking trips as well as for both rock and Winter climbing.
It is obviously hard to be sure but I think the published volumes are pretty accurate. I'm not sure an extra 3-8 litres is sufficient justification to buy a new sack, but I am pretty sure it will be slightly larger.
