G-Technology G-RAID 4TB Dual Thunderbolt Ports for Powerful Data Transfer, Silver (0G02289)(Certified Refurbished) This Certified Refurbished product is manufacturer refurbished it shows limited or no wear and includes a 90 day warranty Ultra-fast, high-performance Thunderbolt interface technology Double the data transfer rates of USB 3.0 and over 12 times faster than Firewire 800 Dual Thunderbolt ports for easy access and daisy-chaining up to 6 Thunderbolt compatible peripherals Time Machine-ready, plug-and-play setup on Mac OS