DS EN 4634:2009 Aerospace Series - Screws, 100 Degree Countersunk Head, Six Lobe Recess, Short Thread, In Heat Resisting Steel Fe-Pa2601 (A286), Passivated - Classification: 900 Mpa (At Ambient Temperature)/650 Degree C Defines the characteristics of screws with 100 degree countersunk head, with six lobes recess, short thread, in heat resisting steel FE-PA2601, passivated, for aerospace applications.