I have used something called BIN (I think?) before would this be OK. I have some rather odd sized (base of wall) exchanges and (base of wall) returns. I have not been able to find them anywhere. I have found the normal 18" (base of wall) exchanges at Home Depot and Sears (made by Hart & Cooley) but these returns are the same type but huge (~36" wide ~6" high). I really don't like them and they look horrible. I figure the best I can do is to paint them. Any ideas of where I might find "special" exchanges/returns?