Thanks for the replies. The battery says “Yin Long” and allegedly has 6800 mAh which is alarming even to a newb like me. I only ordered them together because it all came with a neat case and wasn’t considerably more expensive. That was before I read about the problems with customs with shipped...
Got myself one of those 303's that came with a cheap charger and a 18650 battery that has a weight like it's made out of paper. I ordered both a high quality battery and charger which will hopefully arrive soon. Until then I'd of course like to give the cheap battery a charge with the cheap...