Most of the older Hyunkia manual transmissions were 18mm like Toyota. The engine drain plugs were usually 14mm... like my Ford, Mazda, VW... So, you need to research your specific year/make/model/engine/transmission for more info.Thanks for the list of plugs. Just bought 2 Votex plugs. One for the engine and the other for the manual transmission (I think they’re the same size, or I’ll have an extra)
Here are the common brand websites:
Dimple Magnetic Drain Plugs – All magnets are not created equal

Magnetic Drain Plugs - By Thread Size
Do you know what size/thread your application requires? If so, then you can find it here.
www.powerslutracing.com
https://www.dormanproducts.com/ oil-tite/dorman/autograde at various autopart stores
Nothing wrong with OE magnetic plugs. Hondacura/Toyotus/Hyunkia/Ford/others have various sized OE drain plugs with magnets.
And, I tend to avoid the aluminum threaded ones which strip easily. So, skip the fancy anodized plugs unless OE is aluminum.
There are a couple sellers that even offer plastic drain plugs, with magnets, for vehicles from VW Ford...