Watch Series 9 GPS 41mm Starlight Aluminum with Starlight Sport Loop Features: L1 GPS, GLONASS, Galileo, QZSS, and BeiDou Compass Always-on altimeter Water resistant 50 meters Certified IP6X dust resistant Blood oxygen sensor (Blood Oxygen app) Electrical heart sensor (ECG app) Third-generation optical heart sensor International emergency calling Emergency SOS International roaming High-g accelerometer High dynamic range gyroscope Double tap gesture On-device Siri Ambient light sensor Speaker Microphone Apple Pay GymKit Capacity 64GB Ceramic and sapphire crystal back Specifications: Finish GPS + Cellular Aluminum available in midnight, starlight, silver, pink, and (PRODUCT)RED. Stainless Steel available in graphite (PVD), silver, and gold (PVD). GPS Aluminum available in midnight, starlight, silver, pink, and (PRODUCT)RED. Case Size and Weight 45mm by 38mm by 10.7mm (45mm) 38.7 grams (Aluminum, GPS) 39.0 grams (Aluminum, GPS + Cellular) 51.5 grams (Stainless Steel) 41mm by 35mm by 10.7mm (41mm) 31.9 grams (Aluminum, GPS) 32.1 grams (Aluminum, GPS + Cellular) 42.3 grams (Stainless Steel) Display 45mm 396 by 484 pixels 1143 sq mm display area 41mm 352 by 430 pixels 904 sq mm display area Always-On Retina LTPO OLED display Up to 2000 nits brightness 1 nit minimum brightness Chip S9 SiP with 64-bit dual-core processor W3 Apple wireless chip Second-generation Ultra Wideband chip 4-core Neural Engine Connectivity LTE and UMTS (GPS + Cellular models) Wi-Fi 4 802.11n Bluetooth 5.3 Power Built-in rechargeable lithium-ion battery Up to 18 hours Up to 36 hours in Low Power Mode USB-C magnetic fast charging cable