I think it depends on the rack system. I see a lot of people get clear tubs for their racks, that makes the snakes feel insecure so then you have to add hides. Getting clear tubs kind of defeats the purpose of the rack system if you ask me, a rack system is designed to make things simple with just a water bowl and nothing to wash when cleaning (like hides, decorations, etc..). Go with a solid grey tub and the whole interior will be dark, just like a huge hide. Then the snake will feel comfortable and won't need a hide at all. If you have clear tubs you may need two hides.