ZENITH Pilot Big Date Flyback El Primero 3651 Automatic 42.5mm Watch Wrap & Bypass Rings This 8mm Concave Tungsten Ring Bracelet Size:8.3 IN This 8mm Concave Tungsten Ring with Diagonal Detailing features a concave centerpiece with modern diagonal detailing in brushed and polished tungsten This special model combines traditional artistry with modern technology The El Primero 3652 automatic high frequency chronograph calibre integrates two functions to the 5Hz (36’000 VpH) movement that are a perfect fit for the PILOT: the big date and the flyback function The patented compliant mechanism advances and stabilises the big date’s two wheels in less than 0