4 piece grinders work just like 3 piece grinders but feature an extra compartment covered with a fine stainless steel screen. These grinders are designed for those who want finely ground herbs, but also for those who want to use the kief.
This type of grinder starts with a top magnetic chamber with the grinding chamber below. A fine mesh bottom sits in the second chamber of 4 piece grinders. Razor sharp teeth grind the dry herb into the finest pieces that fall through the second chamber onto the third chamber. The third chamber catches the finest powder from your ground herb, like fine particles including pollens that can be especially rich.