This is a small, inexpensive hand-held viewer for both 35mm slides and negatives. It features a removable front screen to accommodate thicker slide mounts. Slip your 2x2 slide into the top loading slot to view, or, slide your negative strip through the side slot. The viewer has an "ON/OFF" switch and is powered by 2 "AAA" batteries (not included). It also has a user replacable lamp (2.2v 0.25A bulb). The unit measures 4.25 x 2.5 x .75" (108 x 63.5 x 19 mm) and has a 2 x 2" viewing area. weighs only approximately 2 oz.