Protest all you like, but when the annual Apple keynote at the company’s Cupertino campus rolls around, the watch industry stops what it’s doing to listen. Call it a notification device, wearable tech, or whatever you want, but the Apple Watch, as the pinnacle and most popular of its kind, is as newsworthy for traditional watch enthusiasts as it is for all the techies and Apple addicts you know.

This afternoon, Apple CEO Tim Cook and COO Jeff Williams took the stage at the Steve Jobs Theater to unveil the new and improved Apple Watch Series 4. Before going into the details, Cook boasted that the Apple Watch has become “the number one watch in the world” and “redefined what a watch can do for you,” highlighting three areas in particular that the Apple Watch has proved indispensable.

The Apple Watch keeps you connected to the world around you even without your cell phone.

The Apple Watch has become an “intelligent guardian for health” with top-of-the-line heart rate monitoring.

The Apple Watch has become an all-in-one wellness indicator and fitness tracker.

With its ever-increasing ubiquity and all of the above in mind, here’s what you need to know about the Apple Watch Series 4.

The Apple Watch Series 4. Source: MacRumors.com

New Sizes and Faces

The Apple Watch Series 4 is 30 percent larger, now coming in 40 mm and 44 mm compared to previous iterations at 38 mm and 42 mm. The display has been re-engineered to complement the watch’s shape. Despite its larger size, the watch is thinner overall with less total volume than the Series 3. The redesigned user interface (UI) provides “more info and richer detail” with personalizable watch faces that offer up to eight complications on the dial (see above). The new UI will, in particular, streamline the appearance of the maps, photos, and calendar applications. You can also track MLB scores, your flight boarding information, multiple time zones, and nutritional intake on the dial’s face with a variety of apps. The popular “Breathe” ability is now available in three different watch faces as well.

The new “Breathe” watch face takes advantage of the full-size screen.

Enhanced Functionality Courtesy of a Refreshed Design

The Apple Watch Series 4 offers increased performance thanks to a number of new updates. These include the digital crown now allowing haptic feedback, the speaker being amplified up to 50 percent for phone calls and the walkie-talkie ability, and the microphone being moved to the opposite side to reduce echo. The caseback is now constructed of black ceramic and sapphire crystal to allow for radio waves to pass through both the front and back of the watch for improved reception.

WatchOS5 is the Most Powerful watchOS Yet

The updated 64-bit, dual-core processor allows the Apple Watch Series 4 to operate up to two times faster than its predecessors and offers an accelerometer and gyroscope to detect falls. Apple conducted thousands of studies and identified a motion pattern for falls, slips, and trips that determines wrist trajectory. If you haven’t responded to a notification on your watch’s screen within a minute of the detected fall, then emergency services will be alerted to your GPS location courtesy of the SOS functionality.

Improved Health Features

There are three new heart rate features offered with the Apple Watch Series 4. The watch will send a notification for a low heart rate to go along with its previous high heart rate warning, and the watch can screen your heart rhythm in the background to determine atrial fibrillation. Both of those services are made possible through the improved optical sensor. The big news here, and possibly the biggest news of the keynote watch-wise, is the addition of an electrical heart sensor that allows for an electrocardiogram (ECG) to be performed. This is the first ECG product offered over-the-counter and directly to consumers. To operate the test, all you need to do is open the app and touch the crown. The test takes 30 seconds before displaying the results. Previous tests are stored in the health app and are available as a PDF to share with your doctor. All of these abilities have already been cleared by the FDA, and the President of the American Heart Association, Ivor J. Benjamin, was on hand to recognize Apple’s achievement.

Battery Life

The battery life hasn’t changed from Series 3, offering up to 18 hours of power after a full charge.

Cases, Colors, and Bands

Despite the new size, all the previous Apple Watch bands will fit the Series 4. The new watches come in three aluminum cases in silver, gold, and space gray and three stainless steel options in space black, gray, and gold.

Nike + and Hermès Options Return

There are new editions of both the Nike + and Hermès Apple Watches that are optimized for the new screen and size. Notably, the new Nike version includes a sport loop that has been developed with nighttime visibility in mind.

Prices and Availability

The Apple Watch Series 4 will be available with GPS for $399 and with cellular for $499 once orders become available this Friday, September 14. They will be available in store on Friday, September 21. In addition, the price of the Series 3 has been decreased to $279 starting today. WatchOS5 will be available for all previous Apple Watch models, other than the first generation, starting September 17.