This is ER20 High Quality Collet with 6mm Hole.
Specifications:
  • Made from Alloy spring steel and fully hardened
  • All critical collet surfaces are precision ground for accurate fit
  • Works in all ER20 Collet Chucks
  • ER20 collet has a full 6mm range of collapse while maintaining full accuracy
  • ER20 collet has a range :  5.5mm to 6.0mm