Experience reliable printing performance every time you print with this OKI black self-inking ribbon. Get long-lasting, high-quality prints for essential documents with this black self-inking ribbon. With a duty cycle of 7.5 million characters, you can print a lot of documents before having to replace it. This OKI black ribbon is individually packaged and compatible with select OKI dot matrix printers and impact printers, and the easy-to-install design offers convenience. Compatible with Microline 420, 420N, 421, 421N, 490, 490N, 491, 491N printers Black printer ribbon provides crisp, cost-effective printing suitable for a commercial environment Includes one print ribbon Prints up to 4 million characters for fewer ribbon changes Impact print technology offers high-quality prints.