An essential reference source, different, more complete and just better than the Apple Spec online reference. There used to be a version called Apple Spec Database 11-98 (which I downloaded and owned) that included later iMac and G3 info, not included in the 8-98 database. but it got pulled for some reason. I didn't give this 5 stars because Apple no longer supports or upgrades this database in this superior format, that you can "own" and not just browse like the online dumbed down version.