Apple 54Mb/sec 802.11g Airport Extreme wireless networking card for newer Apple laptops and desktop. See below for a list of Apple models that require this type of Airport card. Note that for use in a PowerMac G5, you will require the external antenna.
Also note that although this card is generally used in the PowerMac G4 Mirror Door FireWire 800 range, the very last model Apple produced, the 2003 1.25GHz single processor version, reverted to using the original 11MB/s Airport card, not this one.
Being 802.11b and g standard compliant means that this card is fully compatible with 3rd parts routers and wireless access points as well as Apple's own Airport base stations. Full backwards compatibility with 11Mbps 802.11b routers.