ASUS External Battery Pack for Universal/Smartphones - Silver Premium Zen design -light weight aluminum outer casing for beauty and strength. it's ergonomic feel and a smooth, premium finish gives it a look of luxury. "Style on the go! the ASUS zenpower is designed with anodized aluminum casing to create a Device you'll want to Show off. Choose from a range of colors and cases." Quickly put life back into all your devices with ASUS zenpower. It offers high-speed, high-efficiency charging with up to 2.4a output. Exclusive ASUS power safe technology monitors temperature, controls both input and output voltages, and guards against short circuits to provide you with maximum safety while charging. Rigorously Tested to ensure top quality