#step-counting
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Apple Watch Ultra 4 & Series 12: BETTER HR, Steps & ECG! (All You Need To Know)
Series 12 ($399, frame_0013) and Ultra 4 ($799) share a redesigned optical + electrical heart-rate sensor on the new S11 chip: repositioned photodiodes, larger power-efficient green LEDs, improved ECG electrodes (frame_0005, frame_0009, frame_0011).