These are Associated’s optional Factory Team Version 2 slipper hubs. They are constructed of steel, and designed for Associated’s B4.1 FT, SC10 FT, T4.1 FT, B44.1 FT, and SC10 4x4, they will also fit any B4, B44, T4, and SC10 with the addition of #7486 V2 slipper spring and washer. Just install these on the slipper clutch assembly and you are ready to roll.