Replace your MIO C520 Battery or Keep an Extra Battery on hand as a backup. This is a High Capacity 1150 mAh, Lithium-Polymer Battery that offers even more up time than your original. Works in your MIO C520 unit. Simple, Easy and Inexpensive! You get a New Battery, Video Instructions, FREE Special Tools (necessary for battery installation), AND You also get a full ONE YEAR Money Back Guarantee exclusively when you purchase from us!