18500 Li-ion Battery adapter to replace 3 x AAA cartridge

This is an adapter you can put an 18500 rechargeable battery (or even an 18650 cell) into so that it's snug in the place of a 3 x AAA cartridge, like in a lot of LED flashlights. The lower battery voltage (3.7 for Li-ion vs. 4.5V for alkaline) is pretty much offset by the lower internal resistance of Lithium electrochemistry, so the flashlight appears just as bright.
Electrical safety is up to you; don't use this if you don't understand the risks.
That being said, I haven't had any issues with this in a Utilitech flashlight I got at Lowe's Home Improvement, similar to the one in the photo.
Edit: 3D print pictures up, check 'em out.
Note: It is designed for a 22mm inner-diameter cylinder; I found that it is a bit snug for precisely 22mm (difficult to remove, and you want to remove a rechargeable battery); I might redesign it for a little more flexibility.
I added a new version; it's 45mm tall; as always, you can adjust Z-height in Makerware to whatever you need. I also included a couple new pictures.