iPhone 17 Pro and iPhone 17 Pro Max models in the U.S. feature an antenna window on the top edge of the devices, for mmWave 5G signals to pass through.
The standard iPhone 17 does not appear to have the antenna window, while the iPhone Air does not support mmWave 5G, so it is not on that device either.
All of the iPhone 12 through iPhone 15 models are outfitted with this antenna window, made of glass. However, it was not present on any of the iPhone 16 models, which were the first devices to feature the Camera Control button on the bottom-right edge, where the mmWave 5G antenna window was previously located.
iPhone 17 Pro models have a new design with an aluminum unibody, but radio signals cannot pass through metal. The reintroduced antenna window, which likely remains made of glass or perhaps a tougher Ceramic Shield material, allows for mmWave 5G signals to better pass through the frame of the devices for cellular connectivity.
While all iPhones sold outside of the U.S. lack mmWave 5G support altogether, the antenna window is present on iPhone 17 Pro and iPhone 17 Pro Max models sold in select other countries, such as Canada, Japan, Mexico, and the United Arab Emirates. These are all countries where the devices are eSIM-only.
mmWave is a set of 5G frequencies that promise ultra-fast speeds at short distances, which is ideal for dense urban areas. By comparison, sub-6GHz 5G is generally slower than mmWave, but the signals travel further, better serving suburban and rural areas.
