This is the new Progressive Shock Spring for the MTC2 1/10 EP car. Using the progressive shock springs will improve steering and stability while taming down the aggressiveness due to bumpy TRACK surfaces.
Using the A2540 (7.0T) for the front and the A2539 (6.5T) for the rear, the MTC2 will enter corners with more speed and be able to turn a tighter radius.

For smaller tracks and tracks with slower corners a combination of running the A2540 (7.0T) in both the front and rear is highly suggested.