Product description Purpose Precision wrench spanners designed for ER collet nuts: ER16 and ER20. Use to install, tighten, or remove ER collets and nuts in machining, tooling and maintenance tasks. Key benefits Correct fit: Three sizes match common ER16 and ER20 collet nut dimensions so you get the right tool for the job. Durable construction: Made of alloy with overall heat treatment for hardness and long service life. torque capability: Hardened material and precise geometry allow secure tightening without easily deforming under load. Improved efficiency: The right spanner size reduces slipping and speeds up tool changes in the workshop. Specifications ER16 wrench spanner size: 120 x 20 x 7 x 13 mm / 4.72 x 0.78 x 0.28 x 0.51 inch ER20 wrench spanner size: 135 x 28.5 x 9 x 17 mm / 5.31 x 1.12 x 0.35 x 0.67 inch ER20 wrench spanner size: 140 x 35 x 12 x 20 mm / 5.51 x 1.38 x 0.47 x 0.79 inch Material and performance Material: quality alloy. Heat treatment: Overall heat treatment increases hardness and wear resistance. Performance: Built for repeated use under torque; resists deformation and maintains fit over time. Compatibility Intended for ER collet systems (ER16 and ER20). Use these spanners with matching collet nuts and holders for secure, correct engagement. Typical applications CNC tooling: Quick and reliable collet nut changes during CNC setup and tool swaps. Maintenance and : Tightening and loosening collet nuts during machine maintenance or assembly. Workshop fabrication: Use in general machining, drilling, milling, and fastening operations that require ER16 or ER20 collet handling. Usage tips Select the correct size spanner for the collet nut before applying torque to avoid slippage or damage. Inspect spanner contact surfaces periodically and if worn to maintain secure engagement. Use appropriate torque and follow machine manufacturer recommendations when tightening collet nuts. What makes it stand out Precise sizing for ER16 and two ER20 variants, heattreated alloy construction, and a focus on durability and torque performance make these spanners practical tools for professional and hobbyist machine shops.