Well, I have been reading all the posts about calibrating your battery and the advantages that it has. My laptop is almost 4 yrs old and I have only done this once and my battery health is 86% and I have posted 194 cycles. Since i want to calibrate my battery, I looked at the Apple website, but have run into a small snag. There are two methods and to differentiate, I need to know what type of SD I have. Now, how do I tell the difference between SD and double-layer SD? My model # is A1095, and looking on the box it only says Superdrive. Also, running a search online, I get this (for media options): 4x/8x/16x/8x/24x DVD-R/CD-RW SuperDrive My computer is a PB G4 1.5 GHz, and I am wondering if anyone can enlighten me- would it explicitly say double-layer, or is it implied, or differentiated by read/write values?