18mm to 26mm Battery Adapter (such as adapt 18650 to 26650)

I purchased a Nebo 6000 against my better judgement. The light is spectacular but the charge port (micro B /cringe) lasts for a finite amount of charges before damaging either the cable (easily replaced) or the port itself. The battery pack it uses are a pair of 26650 batteries bonded with nickel strips and a protection circuit which I presume prevents overcharging. As I wanted to salvage the now unchargeable batteries, I removed the circuit leaving the batteries and used my generic lipo battery charger to recharge them (reconditioned too $$). I wanted to pick up some additional 26650 batteries so I could just swap them out and recharge when needed but to get decent ones seems rather difficult. Fortunately I had a boatload of 18650 cells scavenged from other items available to me which are more than enough to run the light at full power (albeit for a shorter run time) so I created these adapter/shims to allow the 18mm batteries to be used seamlessly in place of the 26650 ones. I also made them short to make them easier to work with, allows a little bit of storage if you're so inclined, and flexibility to use with other batteries pairings such as the 18500 -> 26500s.

Is a simple sleeve adapter with nobs to keep them snug to battery. I've used them (at least with my light) with batteries between 18mm - 18.5mm in diameter with no problems.

Filament choice is optional. I printed my initial ones out of PLA purely because it's what I had loaded and they work great but something like PETG or ABS with it's springy behavior would probably be superior in the long run. I would recommend no more than 3 outer shell layers to allow at least a limited amount of hollow inside to make it more flexible (fill can be anything relatively low).