Check out Fujinet's websites for details, but I love this thing

It boots from the moon, or anywhere there's WIFI. I've booted OS-9 and NitrOS-9 from the SD card and from Fujinet TNFS servers that have COCO content such as ATARI8.US. You can have four drives mounted at the same time, plus whatever physical floppy drives you may have.

Fujinet for COCO serves as a full-on peripheral suite for the Color Computer line. My COCO 1, running at the slowest speed of 38k baud turns out to be on-par with my floppy controller and drives. With a COCO3 it would be super-fast. As it is, performance is on-par with my floppy controller and drives. The actual data rate is slower, but there is zero latency with Fujinet, which compensates.

Compatibility is great. Drivewire has been a COCO staple utility for many years and so the vast majority of software likes it fine.
I've booted and run Flex, OS-9, NitrOS-9, and good old Basic. Fujinet for COCO gives you all the disk storage you could possibly need, it also supplies network access to collections of software you can use directly, without downloading or fiddling with sd cards. It DOES have an SD slot, so even if the 'net is out, you can work with the contents of that. Just stick your files on a micro-sd card and insert it into Fujinet.

Fujinet supplies extended Basic, like a floppy controller does, and supplies a DOS as well, but this DOS is enabled such that you can book from Drivewire devices. It also supplies menus allowing you to connect to your home wifi network, enter servers you'd like to access into a table, and select files from those servers to act as local disks for your COCO. Installation is as simple as plugging in the Fujinet cartridge, and then plugging the 4-pin cable from the Fujinet into the Rs232 port on the back of your COCO. You select via dip switch block which COCO you are using with Fujinet, 1, 2, or 3.

This is a great device, really well-made, an incredible value in peripherals, and gives new life to my old Color Computer.