This is an optional RC4WD Mini 12mm Wheel Widener Set. These work with on any 12mm back hex wheels, such as those on Tamiya F-350, Tundra, Jeep, Axial AX10, Losi Crawler, RC4WD Timberwolf, and Bully vehicles.
Features:
CNC machined widener
Stainless steel mini barrel nut
Widen 15mm each side of the truck
Specifications: OD: 0.51 in / 13 mm Width: 0.04 in / 1.1 mm Internal diameter: 0.24 in / 6.2 mm