Features:* This kit includes a shank extension and 7 spring-loaded collets.* .* The arbor extension allows you to process deep holes.* An ideal replacement for an old or worn one.* The extension is designed to eliminate imbalance and increase safety during cutting and milling.* It is widely used in boring, milling, drilling, tapping, grinding and other processes. Specifications:* Total height: approx. 18mm* Outer Diameter (Max): Approx. 11.5mm * Gripping Range: 1 - 7MM (1mm,2mm,3mm,4mm,5mm,6mm,7mm)* Fits Metric Shank Sizes: for example, 1mm collets fit 1mm metric shank, 2mm collets fit 2mm metric shank.* Material: 45 carbon steel * Color: Silver (as pictures show) Package Contents: 1*8pcs Spring Collets and ExtensionNote: The actual colors of the item may be slightly different from the pictures shown on website caused by many factors such as brightness of your monitor and light brightness