Just tried it today with an ESP-01s and the hardware worked flawlessly nearly (see below) out of the box. But... the hardware is great. Totally recommend it.
Important: Contrary to the usual DIY-philosophy :-) ... one should really take a look on the hints in the description. It took me 10 minutes to figure out that I have to set the reset "Reset Method" to "nodemcu".
I needed something I could easily take with a few spare parts and tools 'in case' I needed it. I wanted small and protected. This certainly fits the requirements. I opted for the printed case version. The voltage switch is a bit recessed, requiring my fat fingers to get a hold of a nail or small screw driver to change it -- which is good, no accidental voltage changes. it would be a lot smaller w/o the cover,but if you're going to toss it into a tool bag, the cover really helps protect it. The only thing I think it's lacking is a power or activity light. One thing worth mentioning (it is visible in the picture) is that the header onboard is female, not male as it typically is. I am going to swap it out (if it can be) for male headers. I have not loaded it up to see how many amps it can handle; but it looks well built, so I have a sufficient level of trust that it will work as advertised.
Great little device, it tests great so far, I don't have a project in mind for it yet, but pan to use it soon on something cool, maybe use it on a solid state relay to unlock a magnetic door lock as the blkbox is very small and can be hidden easily for a backup when I loose my rfid (or forget the password lol)
addendum I have used it since for flashing a few esp8266 boards to disconnect power since it fits on the breadboard so easily in such a small space just hold down the gpio pin low button and toggle the switch
This product is a shallow tray that holds the Arduino board securely and protects the bottom of the board. The base is nicely finished and has labels on the sides for connectors. Shipping was prompt. No documentation necessary.