You will need a screw smaller than 1/4" threads for these caps to fit
I thought these would be the perfect accompaniment to the mirror cowboys plate on front of my truck, in lieu of the hex head screws there, but (after looking at several vehicles) most screws are too big to fit in the rubber receiver, I managed to squeeze mine in there, but then the caps would not 'snap' on. I don't know how well the decorative caps would have 'snapped' on or if they would last under normal conditions