In CMBS, the generic term applied to Certificates of Ownership of the funds or assets of a trust fund. These undivided interests are issued by the Trustee in amounts of $100,000 until less than $100,000 remains, then in amounts of $1,000. The Certificates are usually issued in lettered classes starting with Class A. There can be many classes if there are many different rated tranches in a CMBS. Each class is risk-rated by a rating agency such as Standard & Poor's. If the higher risk first-loss class is included in the security and sold instead of being held by the seller, the class is rated as "NR" (not rated). The "not rated" risk-rating is used for securities not qualifying for the minimum risk rate of B-.