Zyxel USG FLEX 500 Security Firewall The latest USG FLEX 500 provides a comprehensive management platform in the cloud while extending and strengthening protection from firewalls to APs with automatic responses. The redesigned USG FLEX series is able to minimize computing power consumption and maximize firewall performance. It offers up to five times the UTM performance with the flexibility of the cloud and collaborative protection to connect and secure small or medium-sized businesses.