These are Two Replacement Header Pipe Springs for round exhausts. / It is for use with the T-2040 Silencer Set that"s recommend for hte .21VZ-R. / / FEATURES: Steel Construction / Both ends of spring have a hook / / INCLUDES: Two Muffler Springs / / REQUIRES: Nothing. This is a direct replacement part. / / SPECS: Length: 40mm (3.0") / Spring diameter: 3.8mm (0.15")