The answer is ABSOLUTELY NOT. Even unprotected cells are about 1.2mm larger in a triple group than the OUTSIDE diameter of the Mag tube, its utterly frustrating. If the Mag tube were 5mm larger so many more choices would work. The only light that can do 3x 18650 is Fivemega's big body 6AA light that I pray will return to production someday. Fivemegas holders hold 3 18650 , but the light can actually fit FOUR 18650 across for NINE point SIX amp hours of battery (9600mAh). Ever hear of a three hour Mag 1185? For a tribore Mag, 3 17670 cells are the way to fly. Newest gen ones are 1500mAh, so three across is 4.5AH in parallel, or for series applications 1.5AH with 11.1V. Also consider stacks of 17500 cells for more voltage.