These snap-together grommets are functional, strong and print without supports.  I have iterated on the design a few times. To ensure a firm lock-in,  the scale of either the hub or grommets may have to be adjusted by 1 or 2% depending on your printer and the filament being used.  The eight-sided hubs are printed horizontally to ensure layer separation doesn’t occur between the grommets.   

The grommets have been used on poly tarps with good results.  The tudor rose face gives an interesting visual.  These are also appropriate for window curtains as well and can be scaled by 2 or 300 percent.   I have included various hub lengths to accommodate different thicknesses of material between the grommets. Comments and feedback appreciated.