These are special made NAS 1351C4H16 aerospace socket head cap screws in 302HQ stainless steel material. They are manufactured domestically within the USA using DFARS compliant material with production running at typically 50,000 to 60,000 pieces. We supply these NAS socket screws to our long time aerospace customer at revolving annual blanket purchase terms. 1/4-28 UNRF-3A thread to MIL-S-7742 thread specification is incorporated and a minimum hardness of 80 HRB is maintained. All applicable certifications are provided to our customer with each release.