RPM Black The RPM combines a sleek athletic appearance along with the rugged durability found in the comprehensive line of Snap-on footwear. The RPM features high quality water resistant full grain leather uppers. Removable Smartmask sock liners tame the harsh impact delivered when standing on concrete floors. Smartmask sock liners have a molded arch and heel support to provide foot stability and reduce lower body discomfort. The RPM utilizes Cosmo Combat lining throughout the interior of the shoe for excellent abrasion resistance and moisture management. The outsole of The RPM is non-marking as well as gas, oil and grease resistant. The wide channel tread design of the outsole doesn't allow for the accumulation of dirt, sand and grime.