3 Piece Weed Grinder: two compartments, one for grinding and one for storing. 4 Piece Weed Grinder: three compartments, one for grinding, one for storage, and one for kief complete with a screen. Though they arent popular, there are also 5 piece manual grinders. This type usually has four compartments: grinding, storing, and two for kief.
4 PIECE GRINDERS. Out of all the manual grinders on this list, 4 piece models are probably the best. They feature a compartment to catch your ground buds, as well as an extra compartment covered with a fine sieve to catch any kief or pollen.