Wilwood Caliper-Dynapro Radial (Thin Pad) 1.75in Pistons .81in DiscNarrow DynaPro four piston radial mount calipers combine pure race technology with a new generation of Wilwood performance enhancements. The Narrow DynaPro combines the versatility of radial mounting with a sleek profile, superior strength, and extreme durability in adverse conditions. With an overall weight as light as 3. 58 pounds, the DynaPro has become a favored choice for a broad range of sports, rally, and off road driving applications.