This adapter is to enable use of rigid.ink filament spools with a 20mm spool rod such as that used with the Flashforge Dreamer and Omnimount stand supports. You will need a pair of these for each rigid.ink spool you wish to use. Simply insert one in each side of the spool and then feed the spool rod through the hole at each end.
The benefit of using this pair is that you do not need to print a full 70mm+ wide adapter thus saving printing time and filament.
Print as per the .stl file with the rigid.ink logo on the print bed.