The Apple Watch Series 9 features the powerful S9 SiP chip, an Always-On Retina LTPO OLED display (up to 2000 nits), advanced health sensors (ECG, optical heart sensor, temperature sensing), and new Double Tap gesture, offering 18-hour battery life, up to 64GB storage, GPS/LTE options, water resistance, and available in 41mm/45mm sizes and Aluminum/Stainless Steel finishes, running watchOS.