This is a M3 Locking Acorn Nuts. Screw length is 8.5mm. Accurate design. 4 file formats are attached.Details:Pitch: 0.5 mmHeight: 8.5 mmWidth: 6 mmThread Dia: M3 (3mm)
Custom size and design possible, you have to contact with me. If you want other file formats please contact with me.
Thanks, Mahbub