Replace your Magellan Maestro 4000T Battery or Keep an Extra Battery on hand as a backup. This is a High Capacity 1100 mAh Lithium-Ion Battery that offers even more up time than your original. Works in your Magellan Maestro 4000T GPS. Simple, Easy and Inexpensive! You get a New Battery, FREE Special Tools (necessary for installation), a Helpful Installation Video, AND You also get a full ONE YEAR Money Back Guarantee exclusively when you purchase from us!