I was looking for a good rat/mouse comparison chart and wanted to share this as I could never find one. Gives average weights and the exchange between a mouse and the equivalent sized rat. Some may have seen this before but just thought I would share. Just found most breeders like to feed mice while I prefer rats and was a good reference on switching and what "sized" rat I needed:
http://www.ballophile.com/public/sizes1.jpg