Doctor Recommended! The Keplerian series is unique in that the telescopes can be used in a variety of ways: Can be used for distance, intermediate and near use. Unlimited working distances by simply adjusting the focus (from 20 cm to infinity). It can be used as a hand - held spotting telescope and can be easily mounted in the ESCHENBACH 1631 frames and reading caps 167302 to do hands - free tasks. Features: Magnification: 2.8X Distance and 3.4X Near. Lens Size: 9 mm. Lens Type: Keplerian. Case: Vinyl. Mount: Brushed Metal with Rubber Grip. Lens Material: Achromatic Glass with Multi - Coating. Focal Range: 20 cm+ Visual Field: 12.5 Degrees. Weight: 25 Grams. or .88 oz. #16731