RICHARD MILLE, modified sapphire crystal, top king, Model: RM17-01, Tourbillon wristwatch - The smooth sapphire crystal case design at the front and back is uniquely charming. The base plate and bridge plates of the rm017 movement are made of grade 5 titanium alloy, which is composed of 90% titanium, 6% aluminum and 4% vanadium. It is commonly used in aerospace and automotive manufacturing fields and has excellent biocompatibility and corrosion resistance, enabling the gear transmission system to operate smoothly and efficiently. Both the hollowed-out base plate and the bridge plate have undergone complete and intensive tests to optimize their strength. The power reserve display is located on the scale at the 2 o 'clock position, showing the remaining running hours of the mainspring before the next winding of the watch.