Material: Steel grade 5.8. Mushroom knob black grey thermoplastic. Version: Indexing pin hardened, ground, black oxidized. Note: Indexing plungers are used to prevent any change in locking position due to lateral forces. A new locking position can only be set after the pin has been manually disengaged. A screw-in washer can be supplied to help screw in the indexing plungers. The washer is slid beneath the disengaged mushroom knob so that the carrier pins engage in the slot.