This is a 42 mm extension tube that adds 10 mm of length. The outside diameter is 1.8". The male thread is just under 3 mm long and the female thread is about 8.4 mm deep.
1 Review Hide Reviews Show Reviews
42 MM Extension Tube
Not much to say except it worked as expected. Used with ZWO ASI290 and 50mm Stellarvue finder. Brought image into focus. Quality finish. Smooth threads.