Many of the batteries advertised on ebay have grossly overstated mah claims, particularly those ending with "fire" in their name. AW, Panasonic, Sanyo and Sony are all brands which offer quality batteries, but these are often counterfeited, so be careful with your source. The safest bet is to get batteries from an established ecig vendor. RTD and Super T Manufacturing are two companies that I am comfortable with, and AW IMR and ICR are my first choice.