Nrc eyewear x1 series sunglassesin 1947 a piloted plane exceeded the speed of sound in horizontal flight for the first time ever its name was x 1 this was the inspiration for the nrc x series breaking the barriers the technical barrier the use of sophisticated materials delivers the best quality with regards to the lenses and to amplify the field of vision the frame then became lighter with an adjustable bridge to fit any face and finally the arms were fitted with removable rubber tips a