The TGMK2 Extender allows for the addition of an extra rechargeable 18650 lithium battery (included with the extended body), for a longer light. Simply add the Extender to the MK2 body, insert 2-18650 batteries then reattach the switch.
Primary use is to make the TGMK2 longer, however, you can expect 15 minutes longer run time, provided both batteries are fully charged when put in use, otherwise the run time will drop to the lower of the battery charge. 1-18650 rechargeable lithium-ion battery included. You must have an additional 18650 battery.