Epson ACULASER M8000 series - Manual (Page 119)

3. Remove the duplex unit connector cover.
Note:
Keep the upper option cover, lower option cover, and duplex unit connector cover in a safe place to
prevent from losing it.
4. Install the Duplex Unit as shown below. Make sure that the hooks on the Duplex Unit hook onto
the printer’s tabs and the duplex connector goes into the slot.
EPSON AcuLaser M8000 Series User's Guide
Installing Options 119