Oki C610dtn User Manual page 79

8. Starting with the cyan image drum unit nearest the fuser,
replace the four image drums into the drum cavity, making
sure to locate them in the correct order.
Holding the complete assembly by its top center, lower it into
place in the printer, locating the pegs at each end into their
slots in the sides of the printer cavity.
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– C610/C711 User's Guide