These custom tapered shoulder socket head bolts were manufactured using 4140 alloy steel material with 28-32 HRC hardness and zinc clear finish. The shoulder diameter tapers form 0.78″ down to 0.75″ and the head diameter was set to 1.00 +/-.015″. Underneath the shoulder approximately .55″ of 3/8-24 2A thread was rolled with thread relief allowance of roughly .085″.