This is my first 9v 800mAh rechargeable Li-ion battery. I think I got myself a great deal. Usually just the cheap brand, it will cost me a nice one around 8-10 dollars. And for a fire alarm, it will last but a couple of months. This one came with 3 packs of a battery. it is a price for 2 times purchase and you go have 500x more of uses. What a deal. No more disposable battery life!!