Just hold them at 90° to another pair labelled as carrera sunglasses and if the lenses go dark where the lenses overlap, then your sunglasses are carrera too. If there’s no change, your lenses aren’t carrera.  Or you could ask a computer because computer screens use carrera filters. When your computer is switched on and you have something on the screen – a document, game or anything else – just put on your sunglasses and tilt you head left and right. If you reach a point when the screen goes dark you know your carrera sunglasses for men lenses are carrera. These colours absorb blue light the human eye finds the most difficult and uncomfortable. Contrasts are heightened and a high red factor means traffic and brake lights are easier to see.