On December 20, 2001, Apple Inc. released Mac OS X 10.1.2, the second update to Mac OS X 10.1 "Puma". The build number is 5P48 (5P63 for summer 2001 and flat-panel iMacs, as well as "QuickSilver" (2002) Power Macintosh G4s, and PowerBook G4s with Gigabit Ethernet.) The main enhancements in this update include improvements, new functionality, and expanded peripheral support for Mac OS X. Other improvements were seen in the realms of audio, display, speech, networking and printing.