If you want to connect a camera with a 3″ nosepiece to your ESATTO 3″ or ARCO 3″, just connect the 3″ visual back to the M81 thread of ESATTO 3″ or ARCO 3″ . This adapter has an internal brass compression ring to avoid scratching the inserted nosepiece as well as 3 locking screws (120° separation) for a perfect fit, even for heavy cameras or accessories.