Features:
It offers 1.25 inch mounting sizes on telescope side.
The .M42x0.75mm has an external thread on one end and a standard 1.25" (31.7mm) accessory on the other end.
The inside of the adapter is fully threaded to minimize reflections.
The thread accepts a standard 1.25" eyepiece filter.
Main focus photography - use the camera directly.
Simple Barlow Projection - Use your Barlow and camera above.
Eyepiece projection - Use the eyepiece in the extension tube.
Extended Barlow Projection - Use the extension tube with Barlow (expanding the Barlow projection to make 2 times the Baal to 3 times or more Barlow).

Specifications
Product name: Telescope Extension Tube
Color: black
Material: aluminum
Size: as the picture shows
Sleeve interface: 1.25 inches (about 31.7mm)
Thread size: M42*0.75mm

Note:
Transition: 1cm=10mm=0.39inch
Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid.
Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!

Package Include:(other accessories demo in the picture is not included.)
1 x Telescope Mount Adapter