"The first time I bought this water bottle, I was hesitant about wether it would work or not for my new hampster, because there were no product reviews. This is by far the best water bottle I could have bought for my Crittertrail one because I was having difficulty getting the top off the water bottle. With the adjustable O-ring, you slide it on (you have to roll it on to the water bottle and then slide it where ever you want it) and then put it in the hole of your cage where the water bottle is supposed to be. It also comes with a hanger to hang it from wire cages, but I did not try that on a wire cage. So if you have a crittertrail cage, I would totally recommend this water bottle if you don't like the water bottle that comes along with the cage. It does not leak, twist-off cap, and you can adjust the height for your little rodent. The bottle is durable and isn't to big for any animal that you have. But it probably isn't big enough for a rabbit, guinea pig, or ferret, just smaller animals it should work with. So buy this water bottle! It works!"