The announcement of the new Retina MacBook has prompted a flurry of attention to the USB Type C spec, a story we’ve been following since the port was just a gleam in the USB-IF’s eye. It’s not the first device to use Type C, but it’s certainly the most noteworthy, and it’s the first laptop that insists on using Type C for everything from power to data to display output.

Apple’s spec page for the new MacBook says that this port supports “USB 3.1 gen 1,” which there hasn’t been much discussion about. We know that the USB Implementers Forum finalized the USB 3.1 spec back in 2013, and that it raises the theoretical bandwidth of the USB bus from USB 3.0’s 5Gbps to 10Gbps. That’s not the version of the USB 3.1 spec that Apple is offering.

“USB 3.1 Gen 1” is USB 3.0

USB 3.0 was a major change to the spec. It introduced something called the “Extensible Host Controller Interface,” or xHCI, a single interface that could work with all extant versions of the USB spec. Supporting USB 1.0, 1.1, and 2.0 previously required a mix of different interfaces, but xHCI brought them all together and made it easier to make future additions (hence “extensible”).

USB 3.1, by contrast, is a much smaller change—so much so that the USB 3.1 specification has actually absorbed the USB 3.0 spec. For whatever reason, this has led to some odd name changes. The 10Gbps version of USB 3.1 that you probably think of when you think about USB 3.1 is called “USB 3.1 Gen 2.”

USB 3.0 has retroactively been renamed “USB 3.1 Gen 1,” and it retains a theoretical transfer rate of 5.0 Gbps. The USB-IF has confirmed to us that “USB 3.1 Type 1” uses the same controllers as USB 3.0, so we can expect to see some early Broadwell-based Type C systems like the Retina MacBook come with “USB 3.1” even though they’re using what we have heretofore known as “USB 3.0” controllers. The new Chromebook Pixel, likewise, comes with these 5Gbps Type C ports, though Google’s spec sheet refers to them by speed rather than by a USB version.

The 3.0 and 3.1 specs are so similar that we see why the USB-IF didn’t want to separate the version numbers that much. USB 3.1 is certainly no USB 4.0, at least not by the standards set by USB 2.0 and 3.0. But referring to USB 3.0 as “3.1 Gen 1” rather than “3.0” is confusing—what if Microsoft had relabeled Windows 8.0 as “Windows 8.1 Gen 1” when it released Windows 8.1? Is the iPad Air now the iPad Air 2 Gen 1?

It’s confusing at best and misleading at worst, and other outlets and readers have already seen “USB 3.1 Gen 1” on Apple’s product page and assumed that the new MacBook includes a 10Gbps USB port. USB 3.0 didn’t see wide adoption in many computers, Macs included, until its controller had been integrated into chipsets from Intel, AMD, and the like. OEMs are happy to take advantage of features they get “for free,” but few are interested in adding extra controllers to most of their systems (see also: Thunderbolt).

We’d expect USB 3.1 Gen 2 adoption to follow the same course—you’ll be able to find it in some enthusiast laptops and motherboards that include dedicated third-party controllers, but wider acceptance won’t come until it makes it into chipsets and SoCs.

It’s worth remembering that even though many of these new USB specifications are rolling out all at once—the Type C connector, USB 3.1 Gen 2, USB Power Delivery, and USB Alternate Mode—support for one doesn’t necessarily imply support for any of the others. There will be USB Type C devices that use USB 2.0 or 3.0 (sorry, 3.1 Gen 1) buses and transfer speeds. There will be Type C ports that don’t support Power Delivery, and Power Delivery ports that aren’t necessarily Type C.

As more USB Type C devices begin appearing this year, pay attention to what specifications they support when you buy them. As much as we like what all of these USB specs can do, we wish understanding and explaining all of them was more straightforward.