I also bought these chips from AAAToner for my Lexmark X543dn toner cartridges for USD 28/ea
But after 200 of the 1500 expected pages from my double-refilled Black C540 toner cartridge, my printer
gave a warning: 'Black toner low'
The refilled cartridge black toner level was however at least 70%
I could click that error a few times away. But soon after that the printer stopped working.
AAAToner knows about it.
Nowadays there is a warning on the AAAToner site:
WARNING, WARNING, WARNING !!!!!!!!
DO NOT download or upgrade any Lexmark new software
A better advise would be: DO NOT BUY THAT C540 toner CHIPS