Likely just full height, not double height. What has become the normal height for a 5.25" drive is half height. I've seen plenty of full height 5.25" hard drives, but I don't think I've seen double height (would take 4 bays in a modern computer case, if modern computer cases had 4 bays)
I was going to say "my current desktop has 4 CD-capable bays", but I checked and it's actually only 3 bays followed by unused space (and then 2.5" and 3.5" bays below that).
