The tool in your picture is a heavy-duty single hole puncher.
It is used to make round holes in materials like:
• Leather (belts, bags, shoes)
• Rubber
• Plastic
• Soft metal sheets
• Thick fabric
How it works
1. You place the material between the jaws.
2. The round punch tip (8 mm) presses through the material.
3. When you squeeze the handles, it cuts a clean hole.
What the extra pieces are
The small cylindrical pieces in the pack are punch bits (for example 8 mm). They can be replaced if they become blunt.