[LIST] - Unlockable iPhone Basebands Supported by Ultrasn0w

You can check some of the supported and unsupported iPhone basebands below:

Supported iPhone 4 / 3GS / 3G Basebands:

• 04.26.08
• 05.11.07
• 05.12.01
• 05.13.04
• 01.59.00
• 06.15.00
• 05.14.02 via 06.15.00 » [How-To]
• 05.15.04 via 06.15.00 » [How-To]
• 05.16.01 via 06.15.00 » [How-To]
• 05.16.02 via 06.15.00 » [How-To]

Unsupported Basebands:

• 05.14.02
• 05.15.04
• 05.16.01
• 05.16.02
• 02.10.04
• 03.10.01
• 04.10.01

Alternatively, these Ultrasn0w unsupported basebands can be unlock using the SIM unlocking tool like Gevey SIM and Rebel SIM – a hardware unlock that works on all iPhone Firmware and basebands.

On the other hand, iPhone 3G/3GS users with baseband 05.14.02 / 05.15.04 / 05.16.01 / 05.16.02 will be able to unlock their iPhone by updating its baseband to iPad’s 6.15.00 baseband.

Source: List of Unlockable iPhone Basebands Supported by Ultrasn0w | iPhone Wiki