Focal Clear MG Professional Open-Back Over-Ear HeadphonesClear Mg Professional is the essential pair of headphones for discerning sound engineers and producers. To equip these open back headphones 1 5 8" (40mm) full range speaker drivers with M shaped inverted domes; Focal engineers designed a new material: a magnesium cone. This offers extreme precision. The tonal balance is remarkable, as is the bass articulation and the level of detail across the full sound spectrum.