Editor’s Note: This post is being updated as we learn more.

Among the products announced at Apple’s latest keynote event in Cupertino was the Apple Watch Series 4. While the Watch has gotten some much-needed functionality updates over the years, the latest slew of added features could make the Watch Series 4 worth splurging on — even if you have a Series 3.

Following the trend of smartphones ditching bezels and cramming as much screen space into a device as possible, the new Series 4 features a big edge-to-edge display — in fact its display is 30-percent larger than the Series 3. The display features curved edges that mimic the shape of the case. The overall case size has also been updated, and is now offered in two sizes: 40mm and 44mm. There’s less total volume on the new Watch Series 4 because the case is actually thinner than the Series 3. It will be offered in a Space Gray, Silver and Gold. There’s also a Stainless Collection, which features a polished black, space gray and gold.

The new Series 4 will also work with previous Apple Watch bands, so if you’ve purchased a band that you’re particularly fond of, but want to upgrade to the Series 4, you don’t need to ditch it.

The case back is now black ceramic (the display is sapphire crystal). It allows cell signals to travel through the case back and provides better overall reception. It also features an EKG sensor vs. just heart rate (though an optical heart rate sensor is still included). That’s important, because it means that the Apple Watch can now monitor your heart’s rhythm and not just its rate. Simply on the app, place your finger on the digital crown, creating a closed circuit, and in 30 seconds you have an EKG reading. The Series 4 can let you know if you have an issue (Atrial fibrillation) or if your rhythm is normal (Sinus fibrillation). Apple received FDA clearance for these features, and it’s the first of its kind in a device like this. This allows Appple ot technically classify the Series 4 as a medical device.

Also new, the watch will monitor your heart rate in the background and notify you if it detects an elevated heart rate. As for the digital crown, gone is the bright red spot, replaced instead by a red ring around the edge, a much more refined and decidedly less flashy touch. The digital crown also features haptic feedback for the first time.

With the Series 4, you’ll get up to two times better performance thanks to the new S4 chip. This helps to power the next-generation gyroscope inside. According to Apple, this new gyroscope allows the Series 4 to actually detect a fall. This allows a cellular-connected Series 4 to alert emergency services if you take a fall and are immobile for a minute afterwards. But beyond just the updated hardware, the Watch Series 4 also gets updated software: watchOS 5.

With all of these new features, you’d expect battery life to take a hit, but that’s not the case. It features the same 18-hour battery life as the previous Apple Watch Series 3.

The Series 4 will be available on September 21 for $339 (without cellular) and $499 (with cellular). Apple will continue to sell the Series 3 for $279.