These are Wide Clamp Type Aluminum Wheel Hubs by . Hot Racing,
Fits Traxxas 1/16 chassis cars.

6061-T6 Blue aluminum construction (all parts).
High round cap head screws with a hexagon socket drive insert.
These wheel hubs are fastened with cap screws and prevent the 2x10mm
shaft from falling out as well as realize precise wheel attachment.
.

(4) Wheel Hubs
(4) Shafts
(4) Cap Screws
(1) 1.5mm Hex Wrench

Wheel Hubs 12mm
Thickness: 4.5mm
Inner diameter: 4.0mm