Diamond Grind 40mm aluminum 4-piece herb grinder comes with a lifetime guarantee. This Diamond Grind has a unique diamond-shaped tooth pattern made specific for grinding herbs to just the right consistency. Each Diamond Grind is milled from a solid block of 6061 aircraft grade aluminum, that will strongly resist wear and tear over time. These 4-piece grinders feature a 60-micron stainless steel screen for collecting precious flavorful pollen.