If you're like me, you have a bunch of these Harbor Freight flashlights lying around. The only problem is they require AAA batteries, which run out quickly.
Meanwhile, I have dozens of salvaged 18650 lithium ion cells lying around just waiting to be used, recharged, and then used again.
So I made this adapter. The only non-printed part is a small wire needed to electrically connect the flashlight tube and the flashlight lid. It is inserted into the small hole through the adapter and is pushed down by the threads of the flashlight lid (seen in the top-down photo).
IMPORTANT NOTE: 18650 cells can be dangerous. Use this model at your own risk. I will not be held responsible for any mishaps. Lithium-ion batteries can cause fires, or be permanently damaged by misuse.
The STL needs to be rotated and printed upright.