The 9.5" brooder and grow out pens are very similar, except for the heating element. Some customer remove the heater from the brooder and use it as a grow out pen. With the purchase and addition of a heater, the grow out pen can be converted to a brooder. The heaters are available on our website. The 15" brooder has enclosed walls, the grow out pen has open grid walls so it would not be a good switch.