I know I may a bit late, but decided that I want to give a small review on PA-B4.
Last Saturday, I recieved my PA-B4 Wall charger. This charger now accompanies my PA-B3. I bought this power adapter as my fast charger for travel (School, abroad, library, etc…). I love the small form factor, it is very versatile and can practically carry in your pocket. This is much better that carrying a clunk laptop charger which is clunky and get tangled often times. This is why GaN technology is a big deal. I use it with my HP Spectre X360 (late-2019) laptop. I usually can fully charge my laptop in about 2 hours. One minor things that I have noticed is that it will spark up when plugging into an outlet. Other than that, I love these chargers. Definitely recommend.