This light, compact Sigma lens is less than 4 inches in length with an approximate 2.8-inch diameter. The autofocus zoom camera lens covers the most frequently captured telephoto focal lengths, at an aperture range of f/4.5-6.7. Whether the photographer is a hobbyist or professional, the 100 mm - 300 mm lens for Pentax is simple to use and takes clear, crisp shots. This lightweight zoom camera lens is a great attachment for memorializing sporting events, onstage performances, and outdoor landscapes. For high quality, fast photo-taking, the Sigma lens adjusts focus on its own to any lighting conditions. Featuring original three-group zoom technology, this 100 mm - 300 mm lens for Pentax allows optimum optical performance at long distances. The SLC glass prevents the unsightly color aberration that can sometimes occur in photos captured from far away. This telephoto attachment also possesses a filter diameter of 55 mm, which is compatible with most cameras. For the amateur or advanced photographer, the sturdy, easy-to-carry Sigma lens is an appropriate choice.