3961 Spur Gear 0.8P 68T E-Maxx

Spur gear, 68-tooth (0.8 metric pitch, compatible with 32-pitch) 

Replacement part for these models:

E-Maxx Brushless
E-Maxx
E-Revo
Funny Car
Summit

Accessory part for these models:

E-Revo Brushless