Master rolls for use with risograph gr3770. This is a OEM DRUM/MASTER/COPY CTG/OPC RISOGRAPH brand Drum Supply (MASTER ROLLS) that works with the following printers / machines (GR3770). Product Details: Unit : CN/2 Yield: XX Weight: 2.734 lb Special Order Item: N Machines/Models: RISOGRAPH - GR3770 RSGS2659 . MASTER ROLLS. GR3770. OEM RISOGRAPH Brand.