Includes 1pc of ER16 Spring Collet, Accuracy 0.008mm, Size refers to "inner diameter". Material -- Constructed from high-grade, specially formulated spring steel, known for its consistent performance. Features excellent craftsmanship and strong elasticity. Feature -- The ER16 precision collet set is designed for compatibility with ER-type tool holders, reamers, tool rods, extended rod nuts, fixed drills, and various other tools, offering great versatility and adaptability. Applications -- Great for CNC machines, milling machines, engraving machines, and machining centers, these high-precision spring collets ensure reliable performance. Reliability -- Made from quenched and hardened spring steel, these ER16 collets are meticulously ground both internally and externally. They provide high precision, strong elasticity, secure clamping, and a stable cutting experience, enhancing productivity and efficiency.