3600mAh Extended Battery fits Dell Axim X50 X50v X51 X51v series High Quality, high capacity, light weight rechargeable DC 3.7V Li-Ion 3600mAh battery. Larger size compared with the original battery. A special design battery door is provided as the original battery door cannot be use with this battery. Longer battery life than the original battery that comes with the PDA. Best replacement for the original Dell Axim X50 X50v X51 X51v series battery pack. No memory effect. Can be charged or discharged as needed without loss of capacity.