The FC3215AN32.768K-70NN60KC5 is a low-ESR, compact 32.768 kHz crystal unit designed for sub-clock applications in battery-powered and IoT devices. It features a robust Pb-free metal lid with seam-sealed package and operates across a wide temperature range of -40°C to +105°C, with typical ESR of 35 kO at +25°C and maximum ESR of 60 kO across the full operating range. The device achieves a frequency tolerance of ±20 × 10?6 at +25°C ± 3°C and incorporates a newly redesigned tuning-fork crystal element optimized for low current consumption. Its compact dimensions (3.2 × 1.5 × 0.9 mm) and low power characteristics make it ideal for wireless modules, wearable products, low-power microcontrollers, and battery-powered IoT applications requiring extended operational life.