I got mine “MagSafe” nubbins yesterday and I’m delighted. I had one of the first third party ones (I think by Griffen) way back in 2015 when the original USB-C MacBook came out and it required its own integrated cable that was so stiff it disconnected constantly and the nubbin portion (that connected to MacBook) was huge and stuck out a whole inch.
These new ones are tiny – the nubbin part sticks out a few millimeters and the other part attaches to any USB-C cable. There’s a little blue light that goes one when it’s connected and you can even reverse the direction so it goes on either way. Very cool and works great so far. The magnet seems strong enough to hold but comes off easily.
I am only using it for power. Supposedly it can do data transfer, but I wouldn’t trust that with a magnetic connection – too easy to disconnect accidentally while you’re reading/writing data. It also won’t work for video.
I would also only recommend these for laptops with multiple USB-C ports as the nubbin is so small it’s hard to remove once installed. With a single port you’d have to temporarily remove it to connect a hard drive or other accessory, which would be a pain. I’m using one on my M1 Air and one on my intel-based MBP and since both have more than one port, I can use a different port to hook up drives or a card reader, etc.