• Front side - C-mount (1"-32tpi) female thread
• Rear side - C-mount (1"-32tpi) male thread

Machined from high quality aluminium alloy.

Some C-mount lens adapters have a narrow recession to let a lens reaching infinity focus. This does not allow using large lenses with these adapters.

But if you don't really need infinity focus, you can use such an extender (or few of them, if your adapter is very deep) to bring the C-mount thread over the adapter front surface.

You'll be able to mount any C-mount lens in the result, but it will focus to close distances only, and you will be able to take only macro photos therefore.