This is a spacer for use in the filament draw of a Flashforge Finder or in the internal spool holders of the Flashforge Dreamer. If your filament spool has a hole of 52mm diameter like the small filament spools sold by Bilby 3D (see some examples here: https://www.bilby3d.com.au/DispCat.asp?CatID=19&SubCatID=144 ) simple print two of the spacers appropriate to your printer, slot them in the hole and use the spools as though they are Flashforge branded ones.
The letter engraved into the spacer will remind you of the printer the spacer is designed for. D is for Dreamer and F is for Finder. This is helpful if you are lucky enough to own both of these printers as the spoke is a slightly different diameter on the two printers.
You do not need to use a raft however it may make it easier to remove from your bed if you do.