+1 to everybody here. Don't buy a mechanical (unregulated) mod. I was looking around, that Tuglyfe two-battery box runs about $40.00. For that money you can buy an RX200 which is both far more powerful and a lot safer (you do need 3 batteries, not two). If you insist on a mechanical, use only Sony VTC4 batteries, and don't buy them on eBay because most of them are fakes. Get them from a reputable supplier like Orbtronic, Illumn or RTDVapor. In a (2 battery) regulated mod, I would usually recommend Samsung 25R or LG HG2 or HG4 batteries; same caveat, buy them for a good dealer. If the RX200 doesn't work for you, you can buy a 60 watt iStick for 30 bucks (it needs 1 battery) or the iStick 100 (2 batteries) for about the same price.