The GRAV Grinder features a unique 4-part design with three polycarbonate windows in the central chamber so you can always keep an eye on your stash. The bottom chamber is equipped with a replaceable magnetic pollen screen that can be removed for easy scraping. GRAV engineered the grinder to have an easy-to-grip exterior that provides an effortless grinding experience. This four-piece GRAV Labs creation features 15 well-spaced teeth to evenly chop dry herbs as well as wide holes in the upper chamber to prevent clogging. They are made of high-quality materials and are a great addition to your toolbox.