The Jaeger-LeCoultre Calibre 388 is a hand-wound movement developed and manufactured in-house, based on the patented Duometre concept with two independent gear trains—one dedicated to timekeeping, the other to complications—linked by a single escapement for uncompromised precision. Its most striking feature is the Heliotourbillon: a triple-axis tourbillon composed of 163 components and weighing less than 0.7 grams, rotating in a dynamic motion to enhance chronometric performance and visual spectacle. Calibre 388 incorporates a perpetual calendar with a grande date, moon phase, day/night indicator, and leap year display, alongside dual power reserve indicators. It runs at a frequency of 28,800 vibrations per hour (4 Hz), offers a power reserve of approximately 46 hours, and consists of 655 components including 89 jewels. The movement measures 34.3 mm in diameter and 11.15 mm in height.