The 10th version of the Apple Watch was announced at Apple’s event on Monday and features a 40 percent brighter wide-angle OLED screen that is larger than the display on the Apple Watch Ultra.

The new Apple Watch Series 10 is just 9.7 millimeters thick, making it 10 percent thinner and 10 percent lighter than the Apple Watch Series 9. Apple says the larger OLED screen, the largest ever used in an Apple Watch, allows the wearable to display an additional line of text on the screen, making it easier for users to check emails and messages at a glance.

Powered by Apple’s new S10 chip with quad-core Neural Engine, the Series 10 has a polished aluminum finish and a new metal back that houses the smartwatch’s various antennas. It is still waterproof to a depth of 50 meters and has a larger charging coil that allows for faster charging. The Series 10’s battery can be charged to 80 percent of its capacity in just 30 minutes, while battery life is estimated at 18 hours.

The Series 10 will be the first Apple Watch to feature sleep apnea detection (pending FDA approval), which uses the smartwatch’s accelerometer to monitor the user’s breathing when worn regularly during sleep. Sleep apnea is a condition in which people suddenly stop breathing while sleeping. It is usually detected using devices that monitor the patient’s heart, breathing patterns, brain activity, and even limb movements. If the Series 10 detects signs of sleep apnea, it will alert the user and generate a detailed report that can be sent to a doctor who can make an official diagnosis.

The Series 10’s speakers are smaller to improve the smartwatch’s battery life, but Apple says the change doesn’t affect sound quality. For the first time, the Series 10’s speakers can also be used to play audio files like music and podcasts, rather than just being used as a speakerphone for calls.

Using a built-in temperature and depth sensor, the Series 10 provides snorkelers and divers with information about their diving depth. And as part of watchOS 11, the new smartwatch also includes Apple’s Tides app and improved paddle tracking for kayakers.

The Apple Watch Series 10 will be available in three finishes: natural, gold and dark slate, as well as a Grade 5 titanium version that is 20 percent lighter than the Series 9. It will be available on September 20 and will start at $399 for a GPS-only version and $499 for a version with cellular capabilities.

The Apple Watch Series 10 also comes with watchOS 11, which adds several new fitness features, including a Vitals app, a training load metric that lets you know if you’re above or below your usual activity and exercise levels, and the ability to pause your activity rings so a rest day doesn’t mean the end of a long workout streak.

The 10th Apple Watch arrives after nearly a decade of iterative updates to the company’s smartwatch. Apple initially focused on marketing it as a fashion accessory and iPhone companion, but through hardware upgrades and new features in watchOS, the Apple Watch has since become a major health and fitness tool.

The Series 10 is the successor to last year’s Apple Watch Series 9, which introduced features such as a “double-tap” gesture for answering calls with one hand, a brighter screen, and a new S9 SiP (System in Package) that allows for faster processing of Siri requests on the device.

Previously, the Apple Watch Series 8 featured additional temperature sensors for improved health monitoring as well as fall detection. It was also launched at the same time as the Apple Watch Ultra, which featured a larger screen, additional buttons and a more robust and durable design to compete with products from companies like Garmin and Suunto that focused on outdoor activities.

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