The various batteries you can put into your flashlights. We of Best Light recommend going with an 18650 where possible, but if you need to, we have smaller batteries as well.
AceBeam 10440 Li-Ion Battery
Nitecore 18650 2300mAh Li-ion battery (NL1823)
LG HG2 IMR18650 3000mAh battery
Sony VTC5 18650 2600mAh battery
LG MJ1 INR18650 3500mAh