Old Corrugated Cardboard (OCC) includes most types of corrugated packing, gaylords, etc. Boxboard, Kraft paper (brown grocery bags), carrier stock, cereal and shoe boxes are accepted by the mills if they represent less than 5% of the load. 

Waxed cardboard is not included in this category because it is water resistant. Also excluded is Asian cardboard because the quantity of fiber is minimal and it dissolves as a powder in water. You can recognize Asian cardboard by its yellowish color. 

Newsprint grade fiber includes all newsprints, flyers and inserts. Minimal amounts of magazines are acceptable, but telephone directories are excluded by most mills because of the glue present on the binding.
Low grade mixed paper includes all rejected fibers from the recycling centers. This grade includes all types of fibers like boxboard, telephone directories, office mixed paper, brown Kraft paper, newsprint and OCC and requires minimal sorting. 
The office waste grade comes from the daily operations of companies and includes white paper, newspaper, computer paper, etc. Carbon paper is excluded because it is not made of fiber. 
There are also different printer grades that are categorized and have an added value like unprinted white paper, production clippings, computer paper or glossy paper.
All fibers should, as much as possible, be clean, dry and free of contaminants such as plastic, glass, metal, wood, mud, rock, organic material, dangerous and medical products, etc.