This is the 1/16 GTR FS (Factory Space as TRA) Shock Spring
for the Traxxas 1/16 GTR,

Hot Racing cold-coiled springs are designed as Traxxas GTR Factory Space spring.
Spring Steel construction
7147 = Purple
7148 = Titanium
7145 = Blue

Two Purple GTR Shock Springs
Two Titanium GTR Shock Springs
Two Blue GTR Shock Spring