10-15% is usually a guide for a growing snake. I don't see many people (I've read a lot of these threads) feeding ball pythons anything more than 120 grams or so. 120 grams is the highest end of the weight range of their staple 'natural prey' - the ASF rat. They CAN take larger, but that usually results in feeding strikes. I'd rather feed 8x 100 gram rats at one a week than feed a 160g rat and have them go off feed for 2 months. I had to experience this first hand for it to sink in. I plan to stick to 80-120g rats once a week because of this.