This is an optional Tekno RC 75mm Front Shock Spring Set, intended for use with the NB48 2.0 Nitro Buggy.
This purple spring has a setting of 5.65lbs per inch.
Specifications:
Weight: 0.07 lbs
Dimensions: 4.5x2.5x1in
Tekno RC EB48 2.0
Tekno RC NB48 2.0