Blue vs Gray Trustfire 18650 Cells:
There is scattered debate in the flashlight (torch) community over which is better, blue or gray Trustfire 18650s with passionate lines periodically drawn on both sides.  The difference? The blue ones have been on the market longer than the gray ones. 

In addition to the incredible capacity you get with these 18650 batteries, they also have a protection circuit that guards against over charge, over discharge and reverse polarity.

Gray Trustfire 18650 cells might sometimes be just a touch wider than their blue counterparts.  This is due to the added protection.  This width variation is usually 1mm or less but that might be just enough to make them a tight fit in your flashlight.  Some people will hone the inside of their flashlight tube to allow proper fit.  Some people  remove the outer plastic wrap, which we do NOT recommend, ever.


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