DS EN 4321:2005 Aerospace Series - Bolts, Double Hexagon Head With Lockwire Holes, Relieved Shank, Long Thread, In Heat Resisting Nickel Base Alloy Ni-Ph2601 (Inconel 718), Silver Plated - Classification: 1550 Mpa (At Ambient Temperature)/650 Degree C Defines the characteristics of double hexagon headed bolts with lockwire holes, relieved shank and long thread, in NI-PH2601, silver plated, for aerospace applications.