In order to unlock iPhone 4 and iPhone 3GS on iOS 4.3.3 the Dev Team released ultrasnow 1.2.3. Ultrasnow 1.2.3 is not a new unlock so it does not work on higher basebands like 02.10.04, 03.10.01, 04.10.01 and 05.15.04. But iPhone 4 and iPhone 3GS having basebands 01.59.00, 04.26.08, 05.11.07 and 06.15.00 can only be