Product DescriptionExtender EF 1.4x II_This tele extender can be used with fixed focal length lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, 70-200 f/4.0L IS USM, and 100-400 f/4.5-5.6L IS zoom lenses. Superb optically, it preserves the image quality of the lens it's mounted to and multiplies its focal length 1.4x. Effective aperture is reduced by one f-stop; autofocus is possible on any EOS camera when combined with a lens having an f/4 or faster_..._read more_ture. The new version II maintains the outstanding optics of the previous version, and adds enhanced weather-resistant construction, and improved anti-reflective surfaces in the barrel._Content_1_Main Unit Spec Focal Length & Maximum Aperture Magnification: 1.4x Lens Construction 5 elements in 4 groups Max. Diameter x Length, Weight 2.9 x 1.1, 7.8 oz. / 72.8 x 27.2mm, 220gAmazon.comMultiply the focal length of your 135mm or longer lens by 1.4x without sacrificing image quality with the Canon EF 1.4x II extender. Optically superb, the lens fits all Canon 135mm fixed focal length lenses (except the 135mm f/2.8 Softfocus lens), along with the EF 70-200mm f/2.8L, 70-200mm f/2.8L, 70-200mm f/4.0L, 70-200mm f/4.0L IS USM, and 100-400mm f/4.5-5.6L IS zoom lenses. In addition, the extender doesn't sacrifice your autofocus on any EOS camera as long as it's combined with a lens having an f/4 or faster maximum aperture (the extender reduces the effective aperture by one f-stop). Best of all, this version maintains the outstanding optics of the earlier incarnation, but adds a weather-resistant construction and improved anti-reflective surfaces in the barrel. The EF 1.4x II extender, which measures 2.9 inches in diameter and 1.1 inches long, weighs 7.8 ounces.