There are a lot of good posts here and I think a few of you have the right idea, there really is no set rule, especially with Ball Pythons. I have been keeping snakes for many years. I dont have alot of posts because I am a reader more than a writer.I currently keep mainly carpet pythons now but have 2 Ball pythons and have had others over the years. One of my boys eats small/medium rats every 14 days. any more and he will fast. The other will not eat rats, he will only eat mice and only one at a time, he is my PITA. HA HA So he gets 1 jumbo mouse a week. Sometimes he will eat 2 if I offer it but guess what, if he eats 2 he will not eat the following week. Both of these snakes are adult males and each one weighs within 100-200grams of the other, just shy of 1500 grams give or take. If I insisted on doing things the way the "book says", my snakes would fast and not eat on schedule. I have found Balls to be totally different than the Carpets and Boas I keep, they do things their way, owners wishes be damned. As long as husbandry and environmental aspects are maintained, they will eat when they want and what they want to our dismay. As long as they are a healthy snake and thriving it really doesnt matter whether they eat a 100 gram rat every week or two or a 40 gram mouse every week. Everyone needs to remember that these snakes sometimes fast for 6 months or more with no ill effects. When you factor that into the equation, as long as you are not feeding too small or too few prey items to an amimal that would continue to feed otherwise, you are not harming the animal. More times than not they are in control of how much they eat and they dont care about our rules. The Carpets and Boas on the other hand is a different story. Every one I have ever had would eat a Coke Can if I offered it. Sorry for the extended rant but with the fasting these guys often do and their individual personalities factored in, alot of the prey size rules for Ball Pythons are in my opinion irrelevant. JMHO