SANOXY&reg; 3500mAh Extended Battery + Black Cover for HTC Evo 4G This is a high-quality extended battery! Expect more than 2X the battery life of the original. Comes with back battery cover that fits perfectly onto your Evo 4G High quality at a low price! Don't pay higher prices elsewhere. No need to swap standard batteries in and out anymore--this one should last you longer than you need.