The best thing about these batteries is that they are 1000mAh, and that is very hard to find. That is more then others that I saw that were 300, 600 or 800mAH. The battery stays charged longer due to this. My old batteries had gotten to the point where I had to charge them every three days. The first time I used these Kastar batteries after I charged them, I got 10 days of landline phone use. I am on the second charge now, and I have already gotten seven days, so I expect I will get 10 days from this second charge, too.