18650 rechargeable lithium batteries will allow you to get incredible run time out of the flashlights that can handle them.

Roughly the same size as two CR123 batteries, each 18650 is 3.7V and 2500 mAh and has built-in circuitry that protects against overcharge and discharge.

Note: Not all blue Trustfire 18650's come with a protection circuit even though they are supposed to.  Production lots vary.  We sell only those that we have verified to have this very important safety feature.  You can rest assured that the Trustfire blues that you purchase from us are protected.

Never use unprotected 18650 lithium ion batteries! 
The cost difference is too small and the risk of property destruction and personal injury is too great.

As with all lithium batteries, use extreme caution with charging, use and disposal.