DS EN 3537:2010 Aerospace Series - Nuts, Anchor, Self-Locking, Fixed, Two Lug, With Counterbore, In Heat Resisting Steel, Mos[2] Lubricated - Classification: 1100 Mpa (At Ambient Temperature)/315 Degrees C Defines the characteristics of two lug, counterbored fixed anchor nuts, with a self-locking feature achieved by forming the upper portion out-of-round, in heat resisting steel, MoS[2] lubricated.