Piranha 3 piece acrylic grinders are made using strong acrylic resins. Piranha acrylic grinders provide precision grinding within a light-weight, transparent package. The high level of transparency in acrylic allows you to see your dry herbs as you are grinding them. The magnetized lid ensures a tight-fit during the grinding process. The freshly ground herbs can be used or stored in the air-tight storage compartment on the bottom of the herb grinder.