On an early iPhone 4 I found that the #000 Phillips bit included in the 54 Bit Driver Kit didn't actually fit the screws. However the JIS #000 also in the kit did fit quite well. This is due to the JIS bits "thinner" design to prevent camming out of the slot. Otherwise everything went well. Looking forward to replacing the battery in my other phone that has the pentalobe screws. Glad I got the 54 Bit kit!