As usual, Apple’s latest “S” iPhones offer little cosmetic variation compared to the iPhone 6 and iPhone 6 Plus. That said, there are some notable differences between the new iPhone 6S and iPhone 6S Plus and the straight-sixes.

For one, the 4.7-inch 6S and 5.5-inch 6S Plus are both available in a new rose-gold aluminum style. And to prevent Bendgate: Part II, the new iPhones feature 7000 series aluminum-zinc wrought alloy like the Apple Watch Sport. That’s an improvement from the anodized 6000 series aluminum of the 6 and 6 Plus. That makes the new phones a lot less bendy, and Apple says the latest iterations of its venerable smartphone have more durable glass than ever before.

But as we’ve also come to expect in the inevitable “S” iterations, you’ll find the biggest changes under the hood. And you probably won’t notice them until you pick up a new iPhone and start using it.

Then you’ll see—and feel—those changes right away: Both phones will ship with iOS 9, a significant operating system overhaul that promises deeper app integration with Siri and search, a time-sensitive recommendation engine, and (finally) Apple Maps that include mass transit info. But it’s not all software changes, as the iPhone 6S and 6S Plus have some sneaky-big hardware upgrades.

Perhaps the biggest change is the addition of 3D Touch, a new pressure-sensitive interface that senses the difference between taps, normal presses, and firm presses. It’s essentially the iPhone version of a right-click. Screen sensors let you press just a bit harder on the screen to open sub-menus and quick contextual commands. Apple demoed it with Maps, Mail, the camera, Facebook, Instagram, and Dropbox. Forceful presses launch commonly used features and scan information without leaving an app. And Siri is always listening now; she’ll respond to you simply saying “Hey Siri.”

But wait. There’s more! The new phones feature a camera with the highest resolution sensors of any iPhone in the history of forever, with a 12-megapixel main camera that records 4K video and a five-megapixel selfie camera that captures 1080p footage. Because selfies. There’s also a new Live Photos feature that uses 3D Touch to animate your still images. When you take a picture, the camera records a short burst of 12-megapixel images to create that clip; it also adds a bit of animation to the process of flipping through your Photo roll.

Apple also announced that the phones offer new connectivity options, including LTE-Advanced (LTE-A) compatibility and Wi-Fi that’s twice as fast, according to Phil Schiller, Apple senior vp of worldwide marketing.

Both iPhones are the first to pack the new A9 processor and M9 co-processor. According to Apple, the new A9 is 70 percent faster than the last-generation A8, and graphics performance has jumped 90 percent in the new iPhones.

Apple also claims its Touch ID sensor, the fingerprint reader in the iPhone home button, is faster and more precise. The reader is an important piece of the verification puzzle for the company’s Apple Pay system.

For all the change, one thing remains the same: the 16 gig storage on entry-level versions of the new S. That’s something to think about with these new phones, given that they shoot higher-resolution photos, 4K video, and do that new Live Photos trick. Storage is essential for those bigger files.

Gotta have one? No sweat. You can preorder beginning Saturday, and Apple says they”ll ship September 25. They’ll have the same pricing structure as the last generation of iPhones, but there are also new upgrade programs available. On a two-year contract, the iPhone 6S will go for $199 (16GB), $299 (64GB), and $399 (128GB). The iPhone 6S Plus is priced at $299 (16GB), $399 (64GB), and $499 (128GB).