I bought a Newer Technology NuPower AL12 55.5 Watt-Hour Battery for my Powerbook G4 12" (from OWC). I am not excited about it. First, its silver finish looks different from that of my Powerbook and it doesn't fit very well into its place, i.e. it sticks out at one side from the bottom of my PB (well, about 1 mm). More importantly, its performance has been steadily decreasing over the last 30 discharge cycles. It started out at 5000 mAh, as promised by the company. However, after only 32 cycles this number has decreased to 3300 mAh according to coconut battery. And yes, I did calibrate the battery already multiple times. Just for your information, in case you are thinking about getting one ... of course I may have gotten a lemon.