What size of tri-wing screw driver is needed?
Quote from Brady Cabe:
iFixit has two bit driver kits, both which contain the Y0 bit necessary to remove the screw:
Excellent! Thank you Brady.
Quote from Eric Tiffany:
Are the tri-wing screws actually holding the back, or are these only for the battery retainer? The online instructions Apple makes available for HD replacement for the 17" i7 (here) say you only need a #00 Phillips.
The back only needs the Phillips. If you want to remove the battery, you would need the triwing bits.