This is ER11 High Quality Collet with 5mm Hole.

Specifications:
  • Made from Alloy spring steel and fully hardened.
  • All critical collet surfaces are precision ground for accurate fit.
  • Works in all ER11 Collet Chucks.
  • ER16 collet has a full 5mm range of collapse while maintaining full accuracy.
  • ER16 collet has a range : 4.5mm to 5.0mm.