They come with a small plastic holder than fits on the front of the HDD and is screwed on, which allows you to lock the drive into place. They also come with a couple of extra holders as well. That being said, I'm not sure that they're necessary as each drive has a slot to slide into, the holder just makes it easier to slide it in and remove it. You can probably do without it, although I think you'd have to check with icydock to be sure.