I have a Samsung Galaxy S 4 and my battery was charging 100% than I would leave it off and it would go to 77% than die. I bought this new battery and it fixed this problem. so for someone saying that these battery don't work or something wrong with this your wrong it's been a week and i had this new battery down to 10% and still no problem charged back up to 100%. it works great. now that I can say Great Offer Stock seem to have ( OEM ) battery's and they seem to be OEM Samsung that I know of. i'm happy with them and I will be buying for all my phones. thanks again