This is an adapter to fit a Nikon (with a Nikon F fitting) onto a telescope. We have been using this part for almost 6 months on our microscope now and it still works perfectly. Will work for an Nikon 3100, 3200, 3300, 5100, 5200 ,5300, 7100, 7200, 7300 and so on... I recommend printing a cap as well to make sure that no dust will fall in the microscope when the camera is removed. Something like this: http://www.thingiverse.com/thing:36631