Pixco Pro Focusing Infinity Lens Adapter for Olympus OM lens to Nikon F Camera Adapter Three Screws To use, simply attach the ring to your lens and then the lens to the camera. When you have finished remove both together. Its as easy as that! Camera adapter has no lens element so it does not effect optical performance. The screws needs grinding by yourself if it's too long. Notice: This adapter is different from the regular version, it is not screw on the lens, when you use it, you need to remove your lens's original adapter first. Then install this adapter. And you can use your lens original screws install our adapter on your lens.