The Terrain is designed for our most demanding customers, and its well suited for those who require ballistic and safety protection for maximum coverage in a larger frame. With its polycarbonate lenses and frames constructed from the strongest thermoplastic material available for eyewear (TR90NZZ), the Terrain provides extreme impact resistance, durability, and flexibility in a lightweight package.signed for the most demanding customers, the Summit provides premium ballistic and safety rated protection in a smaller frame than the Terrain. Its TR90NZZ frames and polycarbonate lenses combine to create the same extreme impact resistance and versatility as the Terrain, but with a smaller fit and coverage.