its inexpensive ($18.95) and comes with 4 guppies (fat boys)
It ripped the first night I used it. the backing is make out of cheap plastic like a rain poncho or something. The top of the CO2 tank kept poking me in the back, making it raw after only 30 minutes of use. There are no loopholes for suspenders so you are forced to use the uncomfortable strap that keeps sliding down your waist.
Don't even waste your money. Spend the extra money and get a good backpack. It might be OK if you use it for just the guppies, but its definately not rugged enough to hold a CO2 tank.