The tamron tc x14 14x teleconverter with canon ef fit mounts between the camera and lens to increase the focal length by a factor of 14x designed exclusively for select tamron lenses when used with the sp 150 600mm f5 63 di vc usd lens the teleconverter will give the apparent focal length of 210 840mm lightweight and easily portable the dust and moisture resistant tc x14 is the perfect tool for getting closer to your subjects