Adapter to use 18650 battery in place of a 26650. Test print last night and it didn't quite fit. New upload has slightly larger ID and is a little shorter. I reduced the height to 60mm so that the battery will stick out the end a little. I also made the ID 20mm. Apparently an 18mm battery doesn't fit in an 18mm tube. v2 has an ID of 19mm. The 20mm was a little lose for my test battery. Th 19mm is too tight a fit for one of my batteries (the red coated one)This is just a sleeve 65mm long. It should fit around an 18650 battery. The 18650 battery can then be used in place of a 26650 battery.