The BERNINA #C21 Double-Fold Binder Attachment is used with the Binder Accessory Attachment (required). The double fold binder folds upper and lower tape edge for perfect bound edge. The unfolded tape is inserted through the guide rail, folded under on either side and sewn on with a cover- or chainstitch. For the personal, customized look, the tape can also be self-made and cut. Tapes of 36 mm width result in a finished binding of approximately 10 mm. An accessories holder is required to attach the binder. Compatible with L 890.