Depends on the device. If you are on a mech batteries you should use are:
Samsung INR18650-20R
AW IMR 18650 1600mah (not 2000mah)
MNKE IMR 18650
All of those batteries handle over 20amp continuous draw and over 30amp spikes. I listed them in order of personal preference.
Panasonic CGR18650CH should never go in a mech. Also the AW IMR 2000mah has a much lower amperage output than the 1600 I wouldn't recommend it. Efests haven't had a ton of testing done yet so you are kind of being the guinea pig.
I'd recommend visiting some of the flashlight forums for better information on cells and safe operating conditions.
Edit: For regulated devices the Panasonic is nice as well as the LG 3100mah. Just make sure they can handle more than the amp limit on your device.
Samsung INR18650-20R
AW IMR 18650 1600mah (not 2000mah)
MNKE IMR 18650
All of those batteries handle over 20amp continuous draw and over 30amp spikes. I listed them in order of personal preference.
Panasonic CGR18650CH should never go in a mech. Also the AW IMR 2000mah has a much lower amperage output than the 1600 I wouldn't recommend it. Efests haven't had a ton of testing done yet so you are kind of being the guinea pig.
I'd recommend visiting some of the flashlight forums for better information on cells and safe operating conditions.
Edit: For regulated devices the Panasonic is nice as well as the LG 3100mah. Just make sure they can handle more than the amp limit on your device.