There are a lot of different sizes when it comes down to the actual rodent. A rat crawler, in most cases, would be considered a small rat because when a small rat is pretty small, it looks a lot similar to a larger rat crawler. I'm guessing the hopper rat would be near the size of a rat pup, but I could be wrong. I would just consider purchasing whatever is closest in girth to the largest part of the snake's body (I go by that feeding rule: feed the snake a rodent about the same size as the widest.largest part of the snake's body).