Used on F-15S. 3a thread class right-hand 0.625" thread length 20 thread quantity per inch insert, screw, thread cadmium surface treated coil unc thread series
3b thread class 0.250" thread length 32 thread quantity per inch 2 slots or holes 180 deg apart; t thread, mil-s-8879 anodize housing surface treated unjc thread series
3b thread class 0.260" thread length 32 thread quantity per inch 2 slots or holes 180 deg apart; t thread, mil-s-8879 anodize housing surface treated unjf thread series