I bought this with my Sigma 70-200 f/2.8 lens (see my other ads) but never used it. It’s an optical converter which will multiply your focal length by 1.4 as the cost of one stop of light. So a 70-200 f/2.8 lens becomes 98-280mm f/4.0 on a full frame sensor, or 156-448mm on a crop sensor.
Comes with original packaging, manual, case and front/back caps.