They are for under 12' diameter wood. The battery lasts a real long time and charges fully in about 20-30 minutes. There is an indicator light to show battery life and it is as powerful at the last bar as the first. You can get a 14" bar for it but the 12" is what I would recommend. As you can imagine, my guys were skeptical when they got them. At the end of the first day, they loved them. We do a lot of high end properties where noise is a problem. We will continue to get more, but not Stihl, at least not yet until they improve battery life.
Jeff