NAS 6403 - 6420 Rev. 14
BOLT, TENSION, HEX HEAD, CLOSE TOLERANCE, 6AL-4V TITANIUM ALLOY, SHORT THREAD, REDUCED MAJOR THREAD DIAMETER, SELF-LOCKING AND NONLOCKING, 160 KSI FTU
Data Sheet by Aerospace Industries Association - National Aerospace Standard, 03/31/2016