I just bought a Jetbeam RRT26 which runs much brighter on 2 battery sources, and I have a Olight M3X that I wanted to run in it's shortened configuration. So I ordered 2 KeepPower 18350's and 18500's. They were to long and to thick to fit into any of my lights. This is my fault because I didn't read the dimensions when I placed the order. So I cut the wrap off and took off the protection and rewraped them, now they fit. The batteries seem well made, they are thick because they put their protection circuit over a wrap and then wrap it again. And their wrap is at least twice as thick as as Eagletacs. I should have just gotten IMR's but I wanted the protection and more capacity, oh-well. I just wanted to post this so others wouldn't make the same mistake I did. Check the dimensions!