Genuine OEM Oki Microline 421 Toners

The Microline 421 takes the 42377801 black ribbon cartridge, whose shield stays attached when you install it. OKI's guide specifically warns against removing that shield from the ribbon.

Toner Buzz carries genuine OKI 42377801 black ribbons for the Microline 421 as individual cartridges. Keep an unused ribbon in its packaging until needed, whether you're ordering for the next ribbon change or keeping a spare ready.