IMR
batteries, so called "unprotected"
batteries, are made in both button top and flat top. I have both the Panasonic and Efest 18650s in button top IMR. I also have a number of Panasonic "CH" and LG "HE" in flat tops. They all work very nicely in both the VTR and Vamo. Bad attitude is definitely the "source" for battery advice an information.
The whole "protected" battery thing is, I think, kind of a misnomer. IMR batteries, due to their internal chemistry which is designed to reduce the effects of thermal runaway, are actually "protected" by that very chemistry. Granted, there is no electronic protection circuit, or even a basic fuse, involved but the chemistry of modern,
quality, unprotected batteries provides a level of protection that is quite substantial.
(to be read at double speed)
Just my opinion, worth what you're paying for it. No warranty or guarantee is expressed or implied. The reader explicitly agrees to hold the poster free and harmless from an liability or responsibility. Your results an mileage may vary. I am not a chemist, physicist, engineer or physician nor do I play any of them on TV. I hold no recognized degrees in any area. Proceed at your own risk.