If you decided to buy filament without spools, this spool design is for you. It can adapt depending on what amount of plastic you purchased this time. From 100 meters to 400 meters (1Kg) its width can be adjusted by 4 mm steps. All you need to do is to print both sides ("A" side and "V" side), put filament on one side screw other on and fix in with two or three pieces of 1.75 mm filament.
Spool shape is optimized to consume as small amount of plastic as possible and to be printed without any supports.
I personally used PLA, but any type of plastic should do.
Dimentions:
Outer diameter = 203.2 mm
Inner diameter = 50 mm
Hub diameter = 90 mm
Minimal inner width = 29 mm (spool width)
Maximum inner width = 55 mm (spool width)