The reference stabilized telephoto zoom lens by Canon.Lens Construction: 23 elements in 19 groups (1 Fluorite and 5 UD elements) Diagonal Angle of View: 34° - 12° Focus Adjustment: Inner focusing system with USM. Full-time manual focus available Closest Focusing Distance: 1.2m/3.94 ft. (maximum close-up magnification: 0.21x) Filter Size: 77mm Max. Diameter x Length, Weight: 3.5 x 7.8 in./88.8 x 199mm; 52.6 oz./1490g