Hi :wave:
It is supposed to be 4 x 2 for 2 guinea pigs (and I certainly wouldn't put a single in anything smaller than that. However from my own experience, like bunnies - the bigger the better, especially wth boys.
2 of my boys (brothers) have a 5 x 3 hutch and I wouldn't feel happier with them being in anything smaller - especially when you consider - 2 food dishes, 2 hidey holes...
You may get away with smaller than this with 2 girls, but again I would think the bigger the better.
Hope this helps.