The M42x0.75 thread is divided into an inner and an outer with a double-layer structure. The relative positions of the inner and outer rings are fixed with 3 screws, which can easily adjust the camera angle. The adapters are made to insure the perfect fit. aluminum alloy, which does not damage the telescopes thread, and the 2-layer thickened aluminum alloy is very firm. Full manual operation, manual for manual exposure, aperture priority exposure This adapter gives you the ability to use your irreplaceable lens and saves you the cost of purchasing new lenses.