This adapter kit includes 4 extension tubes with M48 x 0.75 threads (male on one side, female on the other side). The optical length of these 4 adapters is 5mm, 10mm, 15mm and 30mm. The diameter of the barrel is 2" so it fits in standard 2" eyepiece holders, diagonals, focusers. The internal barrel uses an anti reflection thread to absorb and minimise internal reflections.

