By the time my BPs are that size I'm either feeding them jumbo mice or rat pups of similar size if they will take them. Rat pups aren't necessarily better for them, but once they get bigger, if their stuck on mice, it's a pain to have to feed 6-8 mice at a time. I have never weighed a rodent before feeding. They are not so fragile that if the rat is a few grams bigger than the rule they'll puke or not digest right. They are not Emerald Tree Boas.