11's phone case xr can be used, because although the iPhone11 and iPhone xr are the same size, the iPhone11's rear camera is a matrix dual camera, while the iPhone xr's rear camera is a single camera, so the iPhone xr can use the iPhone11's phone case. But it will be more obtrusive, it is still recommended to use a dedicated phone case for iPhone EXR.
Yes, the size of Apple 11 and Apple xr is exactly the same, but Apple 11 is dual camera, xr is single camera, so xr with 11 shell is not beautiful, directly buy xr protective shell better.