Zyxel USG FLEX 500 Security Firewall The USG FLEX 500 offers a comprehensive cloud-based management platform while simultaneously expanding and strengthening protection-from firewalls to access points-with automated responses. The newly designed USG FLEX series is engineered for optimized use of computing power and high firewall performance. It delivers up to five times the UTM performance with the flexibility of the cloud and collaborative protection to connect and secure small and medium-sized businesses.