The Celestron NexYZ 3-Axis Universal Smartphone Adapter fits any eyepiece from 35 mm to 60 mm in diameter including telescopes with 1.25\" and 2\" eyepieces, spotting scopes, monoculars, and binoculars. The NexYZ will also attach to microscopes with the addition of the included adapter ring, which takes the usable diameter down to 25 mm, which is the size of a standard microscope eyepiece. A strong spring and a threaded twist lock provide a two-level strong and secure grip on the optical instrument