70-200mm telephoto zoom lens with f/4 maximum aperture for Canon digital SLR cameras. Fluorite UD lens elements produce excellent optical performance in resolution and contrast. Ring-type ultra-sonic monitor (USM) for quick and quiet autofocusing; lightweight construction. Image Stabilizer provides up to 4 stops of shake correction; water- and dust-proof construction. Measures 3 inches in diameter and 6.8 inches long; weighs 26.8 ounces