We used some tileboard for the inside of our cages, its easier to cut and less worry about when the paint will cure fully. We have the stuff in 3 so far, one already had it when we picked it up and we just built two 3x2's with it. It's about $20 but a little bit goes a long ways. http://www.lowes.com/pd_61082-46498-...roduct_price|0