OKI Duplex Unit. Media weight (tray 1): 75 - 105 gsm, Media size (tray 1): A4, A5, B5You can achieve professional double-sided printing with virtually no loss of print speed, enabling booklet printing, reducing paper usage and saving space.Features:- Simple, easy to attach design- Prints paper weights of 75gsm to 105gsm.- Handles A4, A5, B5 (and supports custom size: width 148-215.9m, length 210-355.6mm).- Compatible with Oki C5600, C5800, C5700, C5900 printers.