This is an adapter to reduce the inner diameter of a Elegoo plastic spools from 72.5mm to 53mm. The adapter was also adjusted so that the thickness of the spool is not significantly changed (1-2mm per side added). This adapter can help the spool to play nice with filament storage containers or accessories that rely on spools with smaller diameters. 

Photo above shows the adapter printed in white so that you can see the space it fills between the filament container axle and the filament spool.

Print settings can be whatever you want. Prints fine with minimal infill.