This is an MIP Shiny CVD kit for the front or rear of the Traxxas Revo 2.5 and 3.3 trucks.  The kit has the parts to upgrade either the front or rear.  If you want to upgrade both the front and rear, please purchase a quantity of "2".  These CVD's provide positive acceleration, eliminate backlash, and are much stronger than stock.  They are rebuildable.  The shiny coating increases durability.  If you want a little more power to make it to the track, or if you are running a high-performance engine, you need this kit.