The Canon 1,4 EF Extender II is a professional grade teleconverter designed exclusively for use with select Canon brand L-Series lenses (focal lengths over 135mm). Doubling the lens focal length, Extender EF 1,4II incorporates incorporates careful lens placement and anti-reflective coatings for high quality optical performance. The converter also features a built-in microcomputer for seamless communication between camera body, lens, and extender. Extender EF 1,4 II maintains high standards not only optically, but also in terms of the rugged weather resistant construction outdoor pros want. Often an integral part of a professional's kit, Extender EF 1,4 II is a very practical complement to compatible* telephoto lenses. Key Features: High quality optics, 7 elements in 5 groups Multiplies focal length by 1,4 Reduces effective maximum aperture by two f/stops EF Mount but only accepts select Professional L-Series lenses Less cumbersome than carrying another large lens Compatible* Lenses include: EF 70-200mm f/2.8L USM EF 70-200mm f/2.8L IS USM EF 70-200mm f/2.8L IS II USM EF 70-200mm f/4L USM EF 70-200mm f/4L IS USM EF 100-400mm f/4.5-5.6L IS USM EF 100-400mm f/4.5-5.6L IS II USM EF 135mm f/2L USM EF 180mm f/3.5L Macro USM EF 200mm f/1.8L USM EF 200mm f/2.8L USM EF 200mm f/2.8L II USM EF 200mm f/2L IS USM EF 300mm f/2.8L USM EF 300mm f/2.8L IS USM EF 300mm f/2.8L IS II USM EF 300mm f/4L USM EF 300mm f/4L IS USM EF 400mm f/2.8L USM EF 400mm f/2.8L II USM EF 400mm f/2.8L IS USM EF 400mm f/2.8L IS II USM EF 400mm f/4 DO IS USM EF 400mm f/4 DO IS USM II EF 400mm f/5.6L USM EF 500mm f/4.5L USM EF 500mm f/4L IS USM EF 500mm f/4L IS II USM EF 600mm f/4L USM EF 600mm f/4L II USM EF 600mm f/4L IS USM EF 600mm f/4L IS II USM EF 800mm f/5.6L IS USM This converter has a UY date code which means it was manufactured in 2010. I purchased it in "like new" condition from KEH in 2011. I have used it infrequently, so it is in excellent shape.