What F/T Feeder Sizes Should I Order for 4 month old BP

[Neal]

My ball, roughly the same size, is eating weaned rats or rat pups.

A weaned rat is about adult mouse size.

A weaned rat is quite larger than an adult mouse. The standard adult mouse is about the size of a rat pup. Unless the adult mouse is like a retired breeder or just a freakish large mouse then it's not going to be close to a weaned rat size.