These are the 5106 15 x 24 x 5mm Ball Bearings for the Traxxas X-Maxx Monster Truck.
Steel construction with blue rubber seals
Used in the front and rear differentials of the X-Maxx
Two 15 x 24 x 5mm Blue Rubber Sealed Ball Bearings
Inner Diameter: 15mm
Outer Diameter: 24mm