I have several 400 mAh Spinners, and I love them! The battery life is not that long, so I carry a couple with me if I'm going to be out and about for the day, but I'm more than OK with that, because I like to carry several flavors in my mini T3s
tanks to go with them! The 650 mAh Spinners are great too, and last longer, but I just love the tiny size of the 400s!