Power Bomb Gas Canister?

[PHX COBRA]

I recently purchased a GBB on ebay and it sais that it comes with a "50g power bomb gas canister".  I have never seen this before so i was wondering if anyone knows what it is in relation to green gas.  I have never seen grams used on a compressed gas before. Hmmm
Here is the link: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 31685&rd=1

Thx
Ben