Just for sharing purposes. Currently the most reliable and stable Amp output will be from Samsung 25r. Other brands are ok but just saying what is the best so far. Brands like efest, nitecore and ect are all 3rd party companies. The buy the batteries that is rejected from all the major companies and just put their sticker on it.. some of them state the output is 30A or 40A, the problem is, this ar just the pulse hits.. the battery wont run at 40A from start to finish. The output is not that stable. Next to keep in mind, there are 2 typea of 18650 batteries. The protected and unprotected.. both are the same battery but the protected ones comes with a chip inside. Think of it as a circuit breaker just incase your batt starts to malfunction during the usage itself.. happy choosing..