Brother HL-8050N - Manual (Page 160)

APPENDIXES A - 2
Duplex Unit (DX-8000)
Install this unit on the printer to enable 2 sided printing.
For the installation procedure, see Installing the Duplex Unit
on page A-16.
Offset Catch Tray (CT-8000)
Install this tray on the printer to enable offset of print jobs to
be output. Maximum capacity is 500 sheets of the standard
paper.
For the installation procedure, see Installing the Offset Catch
Tray on page A-20.