All models in the Encore/ST G4 line made today, except for those with a part number that starts with SG4-C, include a pre-attached heat sink. Products with a part number that starts with SG4-C are for use only in Power Mac G4 Cube, and do not include a pre-attached heat sink.
When installed correctly, the Encore/ST G4 card reusing the Apple heat sink is just as reliable as the more recent Encore/ST G4 card with a pre-attached Sonnet heat sink. Sonnet chose to pre-attach a heat sink to Encore/ST G4 upgrades (except for those with a part number that starts with SG4-C) because we determined that some users did not properly attach the Apple heat sink and clips, and we wanted to make the installation process easier.
