When my snake was young and a hatchling I started him on a hoppe rmouse, then after a month of feedings of feeding one adult hopper, I moved up to an adult mouse and that was when my boy was 18inches in length. When my snake started to want more food (around 24inches in legnth) I started ot feed larger prey. From weaned rat-small rats. When my snake was 30-36inches in length I started my snake on small rats, then when my snake wanted more, I fed two small rats and nothing more, because my snake is perfectly fine and capable of eating 2small rats. I dont want to over feed him. He is 5ft long and can probably take two medium rats, but he really doesnt need to eat too much. People say only feed the same girth or smaller food items for your snakes. But I think you should feed slightly bigger food or until you get to small rat size.