The PRO-4X package is a trim level offered on the Nissan Frontier. It was first introduced in 2004 and offers a variety of features and options for Frontier owners. Some of the features that are included in the PRO-4X package are: off-road tires, skid plates, 4x4 drivetrain, and atransfer case. Additionally, the PRO-4X package offers a variety of exterior and interior upgrades that give the Frontier a more premium feel.