This is one of the my favorite wireless mouse, I am using from almost 1 year. this mouse come with 1 - AA size batteries. I am use regular almost 3-4 hours daily but I am never change batteries, battery life was outstanding. this mouse size was medium, not big and not small very comfortable to hold in hand and use it. mouse weight was just 84 gram. logitech provide 3 year warranty on this mouse. I am very happy with this mouse.