Hi,
I think phrack3r meant a mouse hopper.
I would try and judge it by the thickest part of the snakes body - or possibly try and take a picture with something we can use to judge size.
That said you are the only one looking at the size of the animal so if you think a fuzzy looks to be about the same width as his body I would go with that for the first try and if he manages it with no problems then try a hopper next time.
dr del