Military divers may need equipment which does not reveal their position and avoids setting off explosives, and to this end, they may use rebreathers which produce less noise due to bubbles emitted from the equipment, and few or no bubbles on the surface, and which contain no magnetic components, and the face-mask may be fitted with anti-reflective glass. Some navies have gone further and given their divers special contact lenses instead of face-masks to cut down on the risk of reflection.