a cheap plastic case, often for DIY releases, often clear, sometimes colored though. CSHELL is (or was) a brand, I think, not 100% sure tho...

a couple examples from stores:

https://www.walmart.com/ip/C-Shell-CD-Cases-Plastic-Clear-25-Pack-GSA-7045015547681/744326140

https://www.amazon.com/Red-Color-Clamshell-Case-C-shell/dp/B00641BXLE

https://www.discmakers.com/shop/ItemDetails.aspx?ItemID=CD-020-00021

...and a variant which could likely be included, with smaller hinge:

https://www.amazon.com/Clear-Round-ClamShell-Case-Shells/dp/B006IJAJW6

lastly, a similar concept, but might deserve it's own packaging type, as it's square:

https://psimediastore.com/products/cshell-discsaver-clr

https://maxtekmedia.com/maxtek-ultra-slim-clear-transparent-square-shaped-cd-and-dvd-disc-clam-shell-case-with-lock-single-disc-capacity-durable-and-impact-resistant-pp-poly-plastic-case/