Specification: Style: ER11 Material: High Grade 45 Carbon Steel Total height: 18mm Outer diameter(Max): 11.5mm Gripping Range: 1MM to 7MM (1mm,2mm,3mm,4mm,5mm,6mm,7mm) Fits metric shank size(s): For example,1mm Collet Fits 1mm metric shank,2mm Collet Fits 2mm metric shank. Features: Made of high grade specially formulated spring steel. Hardened and precision ground. Built in self-Release design and tools will never get stuck in holder. Package Included: 7x ER11 Collets