I bought it along with the docking station, adjusted it to my 6D, I'm very satisfied. At distances over 2m there are autofocus misses, 10-20%. But! if you attach a flash with infrared autofocus illumination to the camera, then the number of misses tends to 0 (where the illumination reaches). So, most likely, the device itself misses and not the glass, although on other glasses I have a much smaller percentage of misses.