A herb grinder is a tool used for breaking down cannabis. Cannabis is often sold in large pieces, and if you want to roll a blunt or pack it tightly into a bowl, you may need a herb grinder. Herb grinders allow you to break dry herbs down into smaller, more consistently-sized pieces. Herb grinders come in a small circle shape and may be made with metal, stainless steel, plastic, or wood materials. Grinders have small teeth that hold the dried herbs and break them down using a twisting motion. Herb grinders are also a must-have tool if you want to collect and add kief to your smoking experience. Cannabis grinders also come in different sizes, which affects how much cannabis you can grind each time.