The PBC (Pyrex Bottom Coil) is a bottom coil tank with a Pyrex tank liner so you get all of the benefits of a glass tank, but the outer part of the tank is plastic so it protects the glass. The PBC, using the bottom coil, provides a nice warm vapor, with a superb clean flavor, and reduced wicking issues. Also different is the body design. While the top of the PBC unscrews, the tank is still designed to be refilled from the bottom.
Smok Tech bottom coils are NOT compatable or interchangeable with other manufacturers tanks and coils. Please be sure you are purchasing the correct replacement parts.