10+ everything unknown00101 said.
Ultrafire / _any_fire batteries are often counterfeit, poor quality, can be dangerous. Flashlight kits on ebay that include a battery & charger send the cheapest battery & charger they can get. They are often dangerous straight up. Seen several reports of the chargers dying or blowing up.
I recommend Starry Light SA-22 $24.99 - 880 Lumens, 4x AA, cree XM-L2. USA seller so you can get it quick. You can use alkaline AAs until you get ni-mh rechargables.
In li-ion only get batteries with quality protection. Panasonic NCR18650PF Protected (usa) Imho others should really not be suggesting unprotected li-ion. Mtnelectronics is run by RMM (Richard). Ships fast. Answers questions / provides suggestions on his blf sales thread. Just check that your light isn’t known to stupidly have problems fitting protected batteries. In that case IMR / Li-mn batteries would fit, they are ok unprotected. Panasonic CGR18650CH is IMR. Likely the same battery relabeled with a button top. I’d go button top.