This is a great cover for the water bottle. I previously had the plastic ones which crack when the rabbit knocks them off on to a hard surface. This doesn't crack, it fits any size of bottle and so far has kept the water from going green. I haven't had it long enough to see what it's like in the cold, but it looks like it would be fine. The attachment for holding it on to the cage is a bit too chunky for the wire we have but it's easy enough to improvise by having an extra wire across the wires for it to clip on to.