Zara ankle strap with gold studs 6.5 New with tag!

Missing 1 gold stone but it comees with extra golden studs. Tried on once. Looking for a 6 since this is big even with the foot petals. I normally fit a 6.5 well with the added petals but these seem to run big. Not sure if I'll ever find a 6 so I'm deciding on whether to part with it or not. Even if its big :(