This is a OEM RIBBONS OKIDATA brand Ribbon Supply (PRINT RIBBON) that works with the following printers / machines (ML520, ML521). This is a Ribbon Supply, that has a yield of 4 MILL, and part number is OKI52107001. This OKIDATA ML520 comes with a 100% guarantee and is extremely well priced for value shoppers and business users alike. Perfect for home or office use. Ships fast and accurately. PRINT RIBBON. ML520, ML521. OEM OKIDATA Brand.