What size rack did you order? Babies can go in larger tubs as long as they are cluttered with a lot of hiding places. Otherwise the general rule is the tub's length + width should be longer than the snake's length, though even that can vary depending on the species. You'd want a heavy-bodied snake in a tub with more floor space, but thinner snakes like corn snakes or Savu pythons could go into one that's a little smaller.