Brother MFC-7820N - Manual (Page 146)

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Consumable items
Note
Toner life expectancy will vary depending upon the type of average print job.
Note
There are many factors that determine the actual drum life, such as temperature, humidity, type
of paper, toner you use and number of pages per print job.
Toner Cartridge Life (TN-350) Starter Toner Cartridge : Approx. 1,500 pages*
Standard Toner Cartridge : Approx. 2,500 pages * +
* When printing letter or A4 size paper at 5% print coverage
+ Requires additional purchase
Drum Unit Life Expectancy
(DR-350) Approx. 12,000 pages