Members, I was given a headlamp as a gift and need some help with battery choice. The headlamp is set up to use (2) 18650's and came with a charger. The battery compartment has the RJ-0181 printed inside it. Questions: 1) do I want button top or flat top? 2) do I want protected cells? Thanks in advance for your help. If you need further information about the headlamp to help me choose the correct cells please let me know.