Xeen - Thanks for the heads up about there being an adapter in the box. Yup! It was buried under the lanyard and O rings. Great!

This does open up lots of 18650 options.

Yes: Acebeam’s 21700 does not fit any of my chargers (but its USB charging cord works fine).

Roma58 - Are you getting a performance boost by using the 4000mAh Samsung 40T? I would think it has greater continuous amp output than Acebeam’s 5100mAh provided battery.