According to ferret.com: "PLEASE NOTE: NEW FERRET NATION MODELS (181, 182, 183) ARE NOT COMPATIBLE WITH OLD MODELS (141, 142, 143). HOWEVER ALL ACCESSORIES SUCH AS SHELVES, PANS, COVERS ARE COMPATIBLE WITH BOTH VERSIONS."
The new models are similar to the Critter Nations and don't use screws. So it is a good idea to be sure you know what you are getting when you order or purchase.