I use the 3.5mm headphone/audio jack to connect my speakers to a PC.
the green 3.5mm headphone/audio jack for mine as well. Though I imagine it won't be too long before its usb.
On the new MacBook Pro models, every port is now a USB-C port, which is pointless IMO.
If only the technology would be far enough to properly get replaced, I would understand that.
But at this time, too many devices don't support USB-C, meaning Apple has the right to $$$ you out on buying converters.
This is why I'm thankful I bought a MacBook Pro model before this rather risky change happened.