Milwaukee 4932430843 - EXACT M22 Knockout Punch 

Features:

• Suitable for mild steel and aluminium up to a thickness of 3mm & stainless steel max. 2.5mm
• For use with Knockout Dies

Specifications:

• Width: 22.5mm
• Max thickness:
  • Mild steel: 3mm
  • Aluminium: 3mm
  • Stainless steel: 2.5mm