Zebra DelGuard

Two different DelGuard mechanical pencils. Standard model (top) and Type-ER (bottom)

DelGuard is a mechanical pencil line developed by Zebra.
DelGuard pencils feature a special patented mechanism which protect the lead from breakage caused by both vertical pressure and angled pressure.
The protection system consists on two independent actions:

1. when excessive vertical pressure is applied, the first spring allows the lead to slide inside the sleeve
   
2. when excessive angular pressure is applied, the second spring pushes the sleeve out to protect the lead.

The combination of these two actions makes the lead virtually unbreakable with some limitations:
lead may still break when using softer leads (such as coloured leads; 0.3mm leads in 2B, 3B or 4B; 0.5mm leads in 3B or 4B) or if the lead is extended for more than three clicks.

Animation showing the vertical pressure protection mechanism of DelGuard pencils

Animation showing the angular pressure protection mechanism of DelGuard pencils