This is the Multi rate Spring Set for the Traxxas 1/16 Shocks used on the Slash, and Revo.

Spring Steel Construction
PROGRESSIVE-Rate Springs, PROGRESSIVE-Rate (PRS) allow the optimum spring rate for each application. These multi-rate springs are soft at the beginning to soak up the small bumps, but transitions (crosses over) to the stiff part of the rate to resist bottoming on jumps and other big "hits. "

Two 1.1mm wire Purple PROGRESSIVE Rate Springs
Two 1.3mm wire Titanium PROGRESSIVE Rate Springs
Two 1.22mm wire Blue PROGRESSIVE Rate Springs

Blue
length: (25mm)
Inner diameter: (10.9mm)
Wire diameter: (1.22mm)
Titanium
length: 19mm
Inner diameter: 10.9mm
Wire diameter:1.20
Purple
length: 22mm
Inner diameter: 10.9mm
Wire diameter:1.28