Endoscope Coupler is an image coupling system used to connect the Medical Endoscope to the Monitor. It displays body organ or cell pictures taken by endoscope clearly on monitor screen. The images are bright and clear, the connection is simple, and focal length can be adjusted fast and easy. It main technical specifications as follows: Model Focal Length Point of View Field Focusing Scope S20 20mm 17? ?mm S28 28mm 12mm