Mooch posted this over at reddit and I felt it was important enough to share here for anyone that has one. @Kevin H. I know has a VT75C so wanted to make him aware: Here is what Mooch had to say: An internal part of this mod gets very hot during use. If you use a longer battery it presses harder against this part, deforming the plastic this part is mounted in. This can result in your battery being short-circuited and can lead to the battery bursting. HCigar Statement/Warning: https://imgur.com/a/aK2q0 Shorter 26650's include the iJoy, Aspire, and Golisi. These are also three of the top performers. Other decent 26650's that were shorter when I tested them include the Basen and Brillipower 4500mAh and the Efest 4200mAh. You are responsible for your own safety though! The battery that is wrapped by these companies can change at any time. If you feel your battery is fitting very tightly, even if I mentioned it above, then do not use it! Switch to using an 18650. They are typically much more consistent in length than 26650's. My sincere thanks to Stefan Krismer for sending me that HCigar announcement!