Here are both of the PSU Shroud covers. These go towards the front of the shroud and you've got two options for them - the Extension (installed by default, on the left) and the Low Profile (on the right).
The Low Profile shroud cover appears to have 3 sections that can be removed if you choose to do so. They are connected much like models connected to a frame. They'll stay in place but it shouldn't be too hard to remove them if you want. I don't know why one would, though. At first, it looked like they were removable to provide extra clearance ... but that's not the case. As you'll see, it's not needed.