http://www.dickblick.com/zz150/19/products.asp?
param=0&ig_id=684

I have a large number of the 11 x 14 books, which 
are good for everything up to "movie sized" 
cels.  I have one 14 x 17 book for my REALLY 
oversized cels.  Depending on how oversized your 
cels are, you may or may not need the 14 x 17 
book.