The best way to choose a product is by looking at the PHY(Physical Layer Device) reference design. Try to choose a MagJack® that is as close as possible to the electrical configuration of the magnetics on the reference design (Is it 4 core, 6 core, 8 core, or 12 core?) using the IC cross reference. If a similar MagJack is not available, consult the PHY manufacturer’s application notes or magnetics guide for acceptable guidelines.