Comes with 2.5mm Zirconia balls in the cap. Fits on any standard 8mm stem (requires). Heated with the wand induction heater and some others but otherwise is heated with a torch.   This is basically a cap and bowl only.  It needs a stem or WPA to work.  Metal stems may heat up quickly after repeated use but any 8mm stem should fit.  We are offering a cheap glass WPA to add.  This works great through water.  It is easily cleanable and replaceable if it breaks.