'Breastplates' in the Bible

and they had breastplates as breastplates of iron, and the sound of their wings was as the sound of chariots of many horses running to war;

And thus I saw the horses in the vision, and those that sat upon them, having breastplates of fire and jacinth and brimstone; and the heads of the horses were as heads of lions, and out of their mouths goes out fire and smoke and brimstone.