This is the Front and Rear Ball Bearing set for the Traxxas 2.5, 2.5R & 3.3 nitro engines.
These support and seal the crankshaft. Front Bearing features front rubber seal, since it is exposed to dirt.
One Front Crankshaft Bearing
One Rear Crankshaft Bearing
Front Bearing: 7mm x 17mm (5mm thick)
Rear Bearing: 12mm x 21mm (5mm thick).