Face shields protect the entire face and the large protective surface minimises the likelihood of dangerous liquid splashes penetrating.  Face shields can also be used in conjunction with goggles (protective or corrective), goggles and some respiratory protection equipment. The shields are mounted directly on the user's head or on a protective helmet. The lenses of this type of visor are usually made of tinted polycarbonate or polycarbonate with reflective layers applied, used where thermal radiation is particularly high.