From the ManufacturerThis is a pair of ProTrac Rear Arms Pro-Lines new ProTrac Suspension kit for Slash is one easy to install kit that greatly increases forward acceleration, corner speed, consistency and drivability The critics are ranting and raving about ProTrac The result is almost staggering after my test down at OcRc Raceway We cant recommend this kit enough, says Xtreme Rc car Magazine It all comes down to the numbers According to the stopwatch, my laps were about 1 to 2 seconds faster with the Pro-Line ProTrac Suspension kit system, says Rc car Action Magazine Why ProTrac Faster, more consistent laps Increased Forward Acceleration More Fluid Suspension geometry for Jumping Light WeightRace Inspired Design Increased Tunability Double Jump Durability One Easy to Install Kit Slash is a registered trademark of Traxxas LP