This ONYX toner is compatible with Okidata ( Oki )  C900 series, including C911, C931, C941, &, C942, ES9411, ES9431, ES9541, ES9542, Pro9431, Pro9541, Pro9542 These models use a dry toner-based printing process, so it is ideal for printing envelopes that will be subjected to harsh weather conditions. These long-lasting toner cartridges will print up to 38,000 pages before needing replacement, allowing you to complete projects without wasting time replacing toner. Manufacturer Part Number : 45536422