We started with the 60 model several years ago, whch was great for our 2 cats. We went "catless" for a few years because of a relocation, and recently became parents to 2 cats again. The 120 model is so much better than the 60, especially considering that all the new features fit in the same size unit! Yes, the unit IS large, but so worth the space! Customer Service is wonderful, too! Thanks for another great product!