Self-locking nut

Listed on the following equipment:
Technogym - Bike XT (D220U)
Technogym - Bike XT (D221U)
Technogym - D91PBNUO-AA01NC (Belt) Spin Bike
Technogym - Low Back - ROM-M058-M458
Technogym - Run 600 XT Pro
Technogym - Run XT (D241U)
Technogym - Run XT (D242U)
Technogym - Run XT (D243U)
Technogym - Run XT - D240U

* Images may not be identical to part.