This is a reel for Robox printers. Instead of having third party reel holders on the side of the printer, why not just put your samples or favourite filament to a reel that fits in Robox printer.

'Top' part goes outside, middle facing outside in 'top' part and top (inside part of the reel) at the end. Use appropriate glue to hold them together. I used Silicone Grease (PTFE) on rim of middle part before it was assembled.
I have printed all but current version of the middle. Version I printed I needed to file off excess plastic from inside of the middle bit. Version uploaded has wider curves and I hope it will fit as it is.
Middle part is printed with support and it was quite tricking to be removed from the rim.
NOTE: for ABS plastic don't forget to scale it for 101.7% (102% on Robox)!

New: I've just added BottomSmallIn, BottomSmallOut, TopSmallIn and TopSmallOut parts. With middle of the reel you can create reel that is 1/3 width using only BottomSmallIn and TopSmallIn. Also, at that 'core' you can add TopSmallOut (another 1/3 width outer) and BottomSmallOut (another 1/3 outer - other side of the reel). With all four parts you'll get reel divided in three parts - ideal for samples!