In order to preserve full range focus to infinity, this adaptor has to have no effective thickness. It clips into the throat of the camera and is retained in place with a small leaf spring whivch engages behind one of the bayonet lugs in the camera body. In order to remove the adaptor, this spring has to be depressed using your finger nail or the tip of a ball point pen. In some cameras, the adaptor can seem a little loose. This is not problem as fitting the lens tightens it in place like a captive nut.

The adaptor requires auto lenses to have the A/M (auto manual switches).

The adaptor is NOT suitable for the Pentax M42 ES lenses. These can be identified by a raised block on the rear of the lens that turns as the aperture ring is rotated.