Contrary to announced in the title of the product, this ball is not working! Announced that can support a weight up to 8 kg when I climb over a D90 with a 70-300mm zoom (everything is weighed about 2 kg) and although the ball is struggling to bear the weight, it is not accurate at all. When I made my frame to a focal length of 300 mm, and I squeeze the clamping screws, the camera slightly down from the weight, but 300 mm is 1/3 of your image that came down. It is very difficult to adjust. So the ball with a rather amateur use fairly lightweight device, I highly recommend for an SLR.
