This is the Team Integy Silver Aluminum Front Gear Box for the Traxxas T-Maxx .15, 2.5, 2.5R, 3.3 (model 4909), and E-Maxx (model 3906). This 4-bolt aluminum case is much more rigid than the stock gearbox, and it looks awesome. The additional strength of this will prevent flexing, which will better protect the internal components and increase their life. This is also a great looking upgrade for show trucks.