Herb grinders are used for crushing and grinding dried herbs without the need to manipulate them with your fingers.
They're cylindrical devices composed of two pieces. Both pieces have sharp teeth aligned to grind the herb when they're are turned.
Some grinders have a fine screen or mesh that separates the bottom of the grinder from the herb compartment. This allows small resin glands to pass through the screen and fall to the lower compartment. They are often called pollinator grinders.
Here you'll find a wide range of metal grinders, acrylic grinders, wood grinders and also electric grinders.