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, 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 Maximum Aperture. 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. Magnification: 1.4x. Lens Construction: 5 Elements In 4 GroUPS. Dimensions: 2.9(d) X 1.1(l) Weight: 7.8 Oz.