This is the Top Shaft & Idler Gear Set Losi Mini-T 2.0 made by MIP.
Key Features
Designed to reduce the rotational mass of your car by 65% leading to quicker acceleration and better braking. Delrin Idler Gear reduces rotational noise while improving backlash in the gears Smaller gear patch to minimize drag coefficient which helps lower motor temperatures and longer run times Precision machined from 7075-T6 Aluminum for strength and great wear characteristics