AeroSpaced grinders are CNC machined from a single solid block of high-grade aluminum, resulting in each piece fitting perfectly. No Paint! Colors are achieved through anodization, which also hardens the aluminum. The silver version is polished aluminum. The top piece of every AeroSpaced grinder is held securely in place by an embedded magnet that still allows for easy rotation. AeroSpaced grinders are backed by a Lifetime Warranty!