Apple is unveiling its Apple Watch Series 4 line of smartwatches today. It’s the first major design overhaul of the Watch since its debut more than three years ago, and the changes are immediately obvious. The Watch’s screen now goes nearly edge to edge, thanks to a larger display with rounded edges. There are now two new sizes, 40mm and 44mm, and the larger display, which is 30 percent bigger, lets watchOS 5 show more information through Apple’s built-in app complications. Apple is also overhauling the hardware inside its Apple Watch, including a new built-in EKG scanner.

Apple is using a new dual-core 64-bit S4 processor, custom designed by the company’s silicon team to improve performance. Apple claims performance will be two times better than previous models. Other hardware improvements include an updated accelerometer and gyroscope.

This new hardware allows Apple Watch Series 4 to detect falls and automatically trigger a call to emergency services if you’re immobile for a minute after the fall. Apple Watch Series 4 will also screen heart rhythm for irregularities that appear to be atrial fibrillation, but the real new feature is the ability to take an electrocardiogram (EKG). Apple says the Watch Series 4 will be the first EKG product offered over the counter directly to consumers, and you simply open an app and put your finger on the digital crown to trigger the EKG.

Apple has received clearance from the Food and Drug Administration (FDA) in the US to allow its Watch to be used as a medical device, but Apple’s claim about being the first might not be accurate. AliveCor has been shipping its KardiaBand EKG scanner direct to consumers since late last year, allowing existing Apple Watch users to switch to a $199 watch band with a built-in EKG scanner.

Apple has also updated every part of the watchOS UI so it’s redesigned to take advantage of the bigger display and show more information in apps like photos, maps, and calendar. There’s even a new watch face with eight complications, and other faces that interact with the display. While the display is larger, the overall volume is less than the Series 3 model, and it’s thinner than the previous generation, too.

The digital crown has been overhauled so it now includes haptic feedback, and the LTE red dot indicator is now a ring. Apple has also improved the speaker on the Apple Watch Series 4 so it’s now louder thanks to a redesign. The rear of the watch is now black ceramic with sapphire crystal.

While this is clearly a major redesign of the Apple Watch, Apple has not changed the battery life of the device. It will remain at up to 18 hours of battery life per day, which in regular practice should last for two days of average use.

All existing bands will work on the Apple Watch Series 4, and there are new stainless and gold stainless finishes available. Apple will make the Apple Watch Series 4 available to preorder on Friday, and it will ship on September 21st, priced from $399 for the GPS version and $499 for the GPS + LTE models. Apple is also continuing to sell the Apple Watch Series 3 priced from $279.