Brand new in the original package.  This is MTH item # 20-89009 Premier Proto-Scale 6-Wheel Truck Hi-Rail Wheel Set.  

Convert your Hi-Rail Wheel equipped diesel locomotive power trucks to a Scale Wheeled version. Requires a Proto-Scale 3-2T power truck (sold with 2006 and later models only).

Each kit contains enough wheel sets for (2) power trucks. Wheels are powdered metal with hi-rail treads and flange heights. Pre-mounted on metal axles with one insulated side for use on 2-rail or 3-rail O Scale track systems.