I have 4 different bottles, all go on the outside of the cage; with a a wire hanger that hooks to the outside, so you can just slip off the wire , fill and return to the cage;Most hang low depending on how I hook it in the cage, the buns don't seem to mind, as long as itsnot too low; I also have one bottle that I made my own hanger that goes inside on the 2nd level of the bunny condo; you might have to buy wire or zip ties and create your own hanger;