Why Do Pen Caps Have a Hole? The Surprising Safety Reason Most People Don’t Know

This small design improvement has become one of the most recognized safety features in everyday stationery products.

Another Hidden Benefit: Air Pressure Balance

Besides safety, the hole can also help with air pressure balance inside the pen cap.

When you place the cap on the pen, the small hole allows trapped air to escape. This makes it easier to cap and uncap the pen smoothly without creating pressure inside the cap.

This prevents ink from leaking or being pushed out due to pressure changes.