it depends on the size of the rat. i get my rats from rodent pro and their smalls are 45-85 grams so i weight till my balls are around 450 grams before they get offered a small. i have a few that are around 500 grams but will not take a small they would rather have a large weaned rat instead of a small one. it depends on the snake and their feeding habits. if you plan on breeding your male this year i dont see how he could not reach breeding size.