I'm not much of a snake enclosure builder. To date I've just housed my snakes in steralite boxes. But the recommended size is two-thirds the length of the snake. Balls don't normally get over 5' in length, so I would say 3' in length should be fine. I would suggest checking the measurements on the "Vision Cages" and using their size as a reference. I'm sure that someone with some enclosure building experience will happen upon this thread and correct me if I'm wrong. Good Luck!