The 510-joule rating means your computer, printer, scanner, external hard drive and other sensitive electronic components are protected against strong surges and spikes. This power surge protector with USB ports features full normal mode (H-N) and common mode (N-G\/H-G) line surge suppression. It filters out disruptive EMI\/RFI line noise that can cause equipment damage or data loss and exceeds IEEE 587 Category A and B surge suppression specifications. Features two USB ports that produce 3.1A of combined power to charge your mobile devices, including smartphones, tablets and MP3 players. A top storage shelf holds smartphones and other small devices while they're charging. Three-plug surge protector mounts to a clamp that attaches to most desks, tables and flat surfaces, bringing power and device charging to your desktop. The ten-foot power cord has a NEMA 5-15P plug and fits through the back of the clamp to reduce cable clutter. Tripp Lite will repair or replace any connected equipment damaged by surges, including direct lightning strikes, up to $20,000 for life (valid in the U.S., Canada and Puerto Rico only.)