We already knew that the Verizon version of the OnePlus 8 was unique in having mmWave support, when the unlocked version of the phone doesn't, but it turns out that's not the only hardware difference. The Verizon OnePlus 8 also puts its volume rocker in a slightly lower position, apparently to make room for a mmWave antenna. That means you'll need to make sure cases you buy are made specifically for the Verizon version of the phone.
Left: A T-Mobile OnePlus 8 case. Right: A Verizon OnePlus 8 case. Note how much lower the volume rocker is.
According to schematics included in an FCC listing, dug up by Phone Arena, the tweak in position is due to a mmWave antenna that lives just above the volume rocker on the Verizon version of the phone:
Image via Phone Arena.
"Module 1," which lives on the side next to the volume rocker, is part of the mmWave antenna assembly according to other supplementary diagrams, and we have to assume the change is due to its presence.
Unfortunately for Verizon OnePlus 8 owners, it means they'll need to check explicit compatibility before purchasing some kinds of accessories. Many cases, including those sold directly by OnePlus, will not be compatible with the Verizon version of the phone. That's too bad, OnePlus' first-party cases are great, though Verizon does sell a "Karbon" version of OnePlus's hybrid-style cases specifically for the Verizon version of the phone, among a few other third-party options.
We've reached out to OnePlus, and we'll be sure to update our coverage with more information if any is forthcoming.