Apple just introduced a brand-new Apple Watch, the Apple Watch Series 4

Apple on Wednesday introduced a brand-new version of its best-selling smartwatch: the Apple Watch Series 4.

The new watch - which Apple announced on stage at its annual iPhone event in Cupertino, California - is an update to last year's version, the Apple Watch Series 3.

The new watch has new features like the ability to measure your heart rate with an electrocardiogram, and a hardware redesign that gives it a larger display.

The Apple Watch Series 4 will come in gold, silver and space gray and will start at $399.

Here's a rundown of the specs:

• A nearly edge-to-edge display - the screen is now 30% larger than previous versions.
• New watch faces, including one with up to eight customizable complications, or special features
• The digital crown now has haptic feedback
• The speaker is 50% louder, which means it's better for making phone calls and using Siri
• The back is now made from ceramic and crystal, which means radio waves can pass through the front and back for better cellular reception
• A new S4 chip
• A faster, 64-bit processor
• A new accelerometer and gyroscope that let the watch detect falls
• New heart rate tracking, including a new low heart rate notification and atrial fibrillation detection
• Built-in sensors that let you take an electrocardiogram, or ECG. Apple says it has received clearance from the FDA for its heart rate tracking features
• Like the Apple Watch Series 3, it will be swimproof and have built-in GPS
• 18 hours of battery life
• It will run WatchOS 5, Apple's new smartwatch operating system

The Apple Watch Series 4 will go on sale on TK.

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