If you have one of these Lexmark printers: MS310, MS310d, MS310dn, MS312dn, MS315dn, MS410d, MS410dn, MS415dn, MS510dn, MS610de, MS610dn, MS610dte, MS610dtn then you need to use the 50F1H00 (or 501H) toner in your printer. The 50F1H00 has a page yield of 5,000 pages.
The Lexmark printers have a separate imaging unit. An imaging unit is the same thing as a drum unit. If your printer uses the 50F1H00 toner cartridge, you’ll need the 50F0Z00 imaging unit. The 50F0Z00 has a page yield of 60,000 pages, which is higher than the page yield of the 50F0Z00 toner cartridge. So you don’t have to change your drum unit every time you change your toner.