fuzzy rats

hey i'm about to switch my ball python from mice to rats but i need to know what size of rats to get. Currently he is eating adult mice so i need to know which size rats are equal to the size of an adult mouse or slightly larger than an adult mouse.

P.S. The reason why I want to switch is because the store where i buy mice have an abundance of rats so he charging less for the rats than mice at the moment.

I would try a rat fuzzy, or maybe a weaner. I don't think it would hurt to feed a rat thats just a little smaller than an adult mouse to start, the biggest thing I have noticed when I switched mine was that they tended to be more timid toward rats because they were larger. Hope that helps.....