Firewall Builder 4.0 is a major upgrade, it adds many improvements across all components of the program. To name a few, it adds support for the high availability firewall configurations; improves the way generated script manages IP addresses and adds ability to manage VLAN, bridge and bonding interfaces; the GUI now has undo/redo facility of unlimited depth and can compile a single rule and immediately show the result. There are many other improvements and changes, all listed in the Firewall Builder 4.0 Release Notes.