QCell AT&T Samsung Galaxy S2 / SII SkyRocket i727 3850mAh Extended Battery + FREE Battery Cover! (NOT Compatible with i9100/T989/D710/i777) SkyRocket Extended Battery by QCell! Highest Capacity Battery in the Market! Designed in Canada! Double Your Battery Life! Optimized for Galaxy Series! Comes with Free Battery Cover! DYNAStop overcharge IC stopper built in! Voltage: 3.7V / Premium Quality and Best Material used!