It looks like a regular spring back, as opposed to a Graflok/International type back, so as the others have said, you would need the type of rollfilm back that slips under the groundglass like a regular filmholder. There are some less costly ones made by Calumet, and fancier ones made by Sinar (Zoom, Zoom II, Vario I think, and a few others) and Linhof (Rapid Rollex--not easy to find used, and very expensive new). The Sinar Zoom backs are multi-format.