Battery life on my iPhone 4s was getting short. I purchased the replacement battery kit which had all the necessary tools to make the switch. The new battery charged right up to 100% and has performed perfectly. I am very happy with my purchase!
The instructions were clear and made the installation a snap.
Don't live with a weak battery. Changing it out is a snap. My advice is to put the phone on the charger until it's completely charged before using it.