A clean MRF accepts recyclable  materials that have already been separated at the source from municipal solid waste generated by either residential or commercial sources. There are a variety of clean MRFs. The most common are single stream where all recyclable material is mixed, or dual stream MRFs, where source-separated recyclables are delivered in a mixed container stream (typically glass, ferrous metal, aluminum and other non-ferrous metals, PET [No.1] and HDPE [No.2] plastics) and a mixed paper stream including corrugated cardboard boxes, newspapers, magazines, office paper and junk mail. Material is sorted to specifications, then baled, shredded, crushed, compacted, or otherwise prepared for shipment to market.