This extension tube will allow you to run use additional 18650 batteries on your M2-Z. This is useful for modifying the light for use with 6V LEDs such as the XHP50, XHP70, MT-G2, and 12V LEDs like the XHP35. You should use an FET driver with the LDO option since this light uses a momentary switch.
This is not for use with the stock driver! If you use this with the stock driver and/or LED it will fry it.