This small filament wire clip is totally independent from the spool sides. My current printer -Anycubic I3 Mega- uses 1.75mm dia. wires. I designed the gap as 1.75mm since my printer is producing holes and gaps a little narrower. Thus, I got nice snag fit with 1.75mm filaments. Not all printers are the same. Therefore, you might need to print a sample and see if a size change is needed or not.
For 2.85mm diameter filament, I have no chance to test the design since I ve got no filament in that size in hand.