A 戒指 finger ring is something you wear on your 指 finger in order 戒 to guard against any knives cutting it off. Or 戒 to guard against infidelity, if it is a marriage 戒指 finger ring. In either case, we say the 指 finger part [5] quietly, just like how we usually say 'ring' and not 'finger ring', because it is obviously on the 指 finger!