The U4 Pro has two main improvements over the basic U4 Pro,
1)With a safety lock for both the blade and the screwdriver, we considered customer feedback and complaints to add a locking mechanism to the blade but keep the size almost the same.
2) The carabiner body is unibody. This optimization adds strength and durability to the carabiner itself.

Tools the U4 Pro could be used for, 

1. Keys organizer
2. Keychain carabiner
3. Screwdriver
4. Can opener
5. Paper cutter 
6. Utility knife
7. Measurement Ruler

The blade uses a standard #11 scalpel blade (5 extra included) for easy and simple replacement. The included screwdriver set is S2 steel, you can choose PH0 SL3.5 or T6 T8 set, if you'd like to order a replacement screwdriver set, check this link.