First of all, if your battery has already failed and you are at all in a rush to replace the battery DO NOT do it through the mail. Next, upon opening the package I was put off by the fact that there were absolutely not instructions on how to remove the old battery and install the new one. This replacement procedure is not for the faint of heart. It is a very delicate and tedious process. This was my first iPhone battery exchange and it took me, an experienced electrical engineer almost 4 hours. Next, the kit does NOT contain all the tools you will need. At a minimum you will need a very small jewelers philips screwdriver, and a magnifying glass or something equivalent. I found instructions eventually on the internet that showed how to disassemble the iPhone. It is a very lengthy process. Set up a well lighted area and also an area where a dropped screw smaller than a BB will not get lost. My greatest fear was that I would either misplace one of the very small parts, or reassemble the device incorrectly. I had to eventually trim a plastic tab on the battery so that it would seat properly so that the motherboard would fit in properly. I have found no instructions anywhere about this problem. There are many micro ribbon cables that are disassembled and eventually reassembled. You cannot really tell if it is done properly. I also wondered if the average person would be aware of the problems associated with not grounding yourself properly and thereby causing a static charge to destroy one of the circuits. All in all, I would have gladly paid the additional cost to have an experience person take on the responsibility to do it instead of me. I would not even attempt it again. However, I was successful. The replacement battery is great. It holds a much better charge than the one I had, even when it was new. We will now see how long this battery lasts (the real test).