Who needs 120 cu ft? I don't know, maybe your buddy who is out of air? Also comes in handy if you need to decompress, or jump back in to unsnag the anchor. No need to tap a fresh tank.
Here's a clue, you can get an HP120 which weighs seven pounds less than your LP102.
Here's a clue, you can get an HP120 which weighs seven pounds less than your LP102.