I made this to replace 4 AA batteries with 4 16340 batteries.
I wanted a way to use 16340s to and retaining 80% of the original battery tray. This way i can also use AA batteries if i so wish.
you will have to cut some tabs away in the battery tray.
It requires:
M4 dome nut
M4 Threaded rod
M4 nut
washer