Features: It is specially designed for Samsung Galaxy S4. Ultrathin design, compact and light weight without increasing additional weight of the S4. Adding wireless charging feature by piggybacking it on the battery of S4, it works well with any Qi-enabled charger. Easy to use. The receiver can be attached to the the battery all the time, and it would not interrupt the normal use of the S4.How to use it : Step 1: Open the back cover of Samsung Galaxy S4; Step 2: Stick the receiver card to the mobile phone's battery and the two protuberant touch points must touch the two recesses next to the battery; Step 3: Close the back cover; Step 4: Place the mobile phone onto the Qi wireless charging pad (not included).Note: The receiver needs to work with the Qi wireless charging pad.Specifications: Compatibility: For Samsung Galaxy S4 Input: DC5V, 1A Output: 1000mA Power conversion efficiency: Up to 70% Reaction temperature: -10 ~ 40 degrees Celsius Working heat up range: below 20 degrees Celsius (ambient temperature below 25 degrees Celsius) Working ambient humidity: below 80% Working life: Charge & discharge above 4000 times Receiver size: Approx. 61.5 * 49.3 * 1mm / 2.4 * 1.9 * 0.04in Receiver weight: 7g / 0.2ozPackage list: 1 * Qi Wireless Charging Receiver for S4