Sanwu Blue Laser - Silver Series Batteries?

I ordered a Sanwu Silver 3W and they do not include batteries.
Their site, https://www.sanwulasers.org/product/silver says.......

Double protected Flat top 2*18650 / 2*18350(not included)

Does it have to be flat top? I want to use 18650's but I don't know which brand.
Orbtronic has a ton of choices on Amazon...

What is "double" protected mean anyways? I know they have 'circuits' that protect them....

Thanks. Cheers.

:angel: