56P0648 Fuser Assembly for Lexmark Optra 420T 110V (U.S.A.) New
 
56P0648 Lexmark Optra 420T / IBM 4922000
Laser Printers, 110V Fuser New, No Exchange required with this purchase.
The fuser bonds the toner to the paper using heat.  Fusers have a limited lifetime and must be replaced when worn out or defective. 
Common signs your fuser is failing: toner does not stick to the page, ghosting of images and text, frequent paper jams at the fuser. 
Most modern printers will warn you that the fusers page count life has expired by issuing a reminder to “Replace Maintenance Kit” or something of this nature.

Fusing assembly used in the following monochrome Laser Printer models
IBM,  4922000
Lexmark Mono Laser T Series  420T  4048001 4048002

See this article to fully understand what “Ghosting” is.

New Part Requires NO Exchange of Old Part.