Boron Max Thresh module is typically installed into the front of the concaves. The Boron Max thresh insert has narrower slots than the regular max thresh insert. It is typically positioned at the front of the concave, as it is designed for maximum threshing. It has small holes to allow early separation of already threshed grain, is 180-degree reversible, and is boronized for extended wearability. Boronizing is a thermo-chemical hardening process used to improve the life and performance of metal components and strengthen resistance to corrosion and abrasive wear. Left hand configuration.