2x (Doubler) 4-element Teleconverter multiplies the focal length of any fine optic it's used with by 2x, maintaining the resolution and contrast at a high level. For use with Sony SAL lenses.
Like the product, works ok when it's working. Pins don't always contact so the f-stop loses control and you have to wiggle it a bit for the pins to make contact again. Wish it was a more solid connection so I don't have to worry about missing a shot because the lens isn't connected correctly.
I think it works fine. I am a bit disappointed by the major change to the f stop when using this converter, however, it does give me the ability to change my 300mm to 600mm. For this I am very happy. I consider this purchase to be of value and will continue to use to get those close ups that I could not get before.