Apple on Tuesday officially introduced the Apple Watch Series 3, which comes with a big new feature: built-in cellular connectivity. The watch looks essentially like the first two versions Apple released—now, with a red crown—but it’s the internals that are seeing some big upgrades.

The big story is support for LTE, which will allow users to be reached while their iPhone isn’t around. Apple claims it planned on adding LTE all along, working hard to ensure battery life and size weren’t affected by the new feature. Apple said there are no antennas or SIM cards; instead, the screen acts as an antenna, while there’s now an electronic SIM, which is a fraction of the size of a nano SIM.

Because it features its own cellular connection, the Apple Watch Series 3 will support Apple Music (and likely other streaming music services), and Messages and other communication features, using the same number as your iPhone. It now packs a dual-core processor, and Siri is faster and can talk now. There’s also a W2 chip for Bluetooth and 85-percent faster Wi-Fi.

For fitness buffs, there’s an altimeter, which is great for measuring elevation gain for climbers and alpine sports.

Apple said there will be two versions of the Apple Watch Series 3, one with cellular and one without. The cellular model retails for $399, while the non-cellular will cost $329. The Series 1 is also sticking around for $249. you can preorder the Apple Watch Series 3 on September 15, with retail availability on September 22.