A large cage, at least 24 by 36 by 36 inches, with a secure lock is recommended. The bar spacing cannot exceed 1/2″.   The enclosure should have enough room for exercise as well as a place to hang a pouch or other safe shelter in which your pet can sleep during the day.  Needs to have plenty of toys for enrichment, and a glider-safe wheel is a must.  A cage cover is not required but recommended as they are very messy at times and will help to contain the mess.  I personally use dollar store shower curtains around the sides and back, I find it an inexpensive option that is easy to replace.  Some vendors do make custom fleece cage covers if you prefer that, a large piece of anti-pill fleece will also do the trick.

Below are some links to some great cages.