I would advise everyone to be careful about the inside-the-socket variety, I’ve had one melt before. 
(This is due to the heat generation of the conversion circuitry being next to the probably substandard socket which itself generates heat).
My recommendation would be the PWR+. Not the cheapest, but they deliver the power, even powering higher power laptops such as a Lenovo X1 Extreme, and XPS 15.