With advanced printers like your OKI mono laser machine, you need more than toner cartridges to ensure its continued operation. You also need essential maintenance items like the original OKI 45435104 maintenance kit.Why entrust the running of the OKI B721 (and all other compatible printers) to anything but a genuine 45435104 maintenance kit. Products produced by the manufacturer of your printer work flawlessly with your machine and the OKI 45435104 maintenance kit lives up to the companies reputation.If however you should ever have any problems with the 45435104 maintenance kit, OKI offer a direct warranty, but this is very rarely needed.