o.O That cage is meant for gerbils and hamsters, who in their right mind would put a guinea pig in that? The cages we sell for our guinea pigs at my work, are big enough for me to climb in and lay down inside. Not that I tried it or anything...Anyways.
Either make your own, or get a cage that has at least 4ft of floor space. They like to run in circles around, and expecially if you have 2 adults they need a big enough cage. I used to breed guinea pigs before I had snakes, lol.