Juli Clover, MacRumors:

Before purchasing, it’s worth noting that the ‌MagSafe‌ Duo is not able to charge an ‌iPhone 12‌ model at the full 15 watts supported by the standalone ‌MagSafe‌ charger. Instead, it is able to charge at a maximum of 14W when paired with the appropriate charger.

And:

The ‌MagSafe‌ Duo does not ship with a power adapter.

And:

When paired with the 20W USB-C power adapter from Apple, it can charge an iPhone up to 11W, and when paired with a 27W or higher USB-C power adapter, it can charge at the aforementioned 14W.

Did I mention that it’s $129? And if you noticed, the word “charger” is in the product name. But without a separately priced charging brick, it’s not much of a charger.

To be fair, it is very small, and if small is key (you travel a ton, for example), this is a nice solution. But don’t forget a charging brick.

Here’s a link, if the MagSafe Duo Charger calls to you.

As I said here, the MagSafe Duo Charger feels like the Mac Pro wheels of chargers.