Kanger's Protank sets a standard for high-quality clearomizers. It's metal and pyrex construction makes it the perfect choice for acidic e-liquids.
The ProTank is one of the newer products off the Kanger line. The ProTank is a bottom fed unit with easily replaceable coil heads.
The filling of this atomizer is very similar to other atomizer, except that the bottom of the unit unscrews rather than the top. The threading on the ProTank electronic cigarette clearomizer is 510-style threading, which allows it to be used on most any battery type, eGo or mods. Given the size of this clearomizer, it's generally seen on large battery setups and mods.
The pyrex tank makes this tank a highly sought after clearomizer, since acidic e-juices will not crack this tank. Acidic e-juices, along with certain flavorings (namely, cinnamon and banana) will eventually crack a plastic tank. Also, they may strip the plastic in these tanks. Personally, I don't want to take the risk of vaping plastic, so I stick with all metal and pyrex tanks (such as the Protank) to negate the risk of that happening.