I use the 850 240gb drive to replace the 128gb sands drive in my 2015 MacBook air 11 which actually only supports pcie gen 2 x4, throttling this drive's pcie gen3 x4 top performance. The speed of this drive when installed is measured as read 1400mb/s, write 750mb/s, which is very respectable considering the old platform it runs on. The build quality of this drive is actually more solid than the official drive. The pin is shiny gold plated. It also comes with two necessary high quality screw driver. So no need to buy extra tools.I rely on one 16gb and one 256gb external ssd for installing the OS mojave on to the new drive. I create a full time machine backup before everything. Then I create a bootable installation usb drive with the 16gb following the official guide about creating bootable installation media on Apple website (google create bootable installation Mojave). After the Mojave installation USB drive has been completed, I install the new ssd to the MacBook air. Then I boot from the created bootable usb drive, which goes into a recovery interface. Under the recovery interface, I use disk utility to erase the 850 drive to the required format (just leave on the default setting). After this step the I can install macOS on to the new drive. When the newly installed OS first boots, it will prompt you to backup from a time machine backup. Then simply plug in the time machine backup and leave the rest to the system. After restoration completed, I get a clean installed Mojave machine in a state exactly like where I left off. It boots exactly like the original drive with no black screen or abnormality.This method does not require 3rd party software. But it does need copy and paste command in Terminal. The bottom line is you need a bootable image from which you can restore (install) to the new drive.