Hello
It depends on your ODD.

If you have a 3.5" ODD you can build it into a 3.5" enclosure (for example it is perfect for 3.5" MO drives). But I guess your ODD is 5.25", therefore I'd recommend a 5.25" enclosure. If you have a slimline ODD (like a Notebook drive) you can get a slimlin enclosure.