Fitting 510 thread batteries, the Metal/Glass Wick Cartridge from The Kind Pen is a great choice for holding and vaping concentrates. The combination of metal structure and glass tubing makes this cartridge one of the sturdiest on the market. The dual seal design keeps the tank from leaking. The Metal/Glass Wick Cartridge holds .5ml and has a low resistance of 1.8ohms. It even comes in your choice of color.