Arvid Nilsson 5085205000 external serrated lock washer (fan washer) to DIN 6798 Form A, for M5 bolts, zinc-plated steel. Inner diameter 5.3 mm, outer diameter 10 mm, thickness 0.6 mm. The external teeth bite into the bearing surface to resist loosening under vibration. Manufacturer's own designation: Arvid nilsson 5085205000 D6798A 350HV-EL 5 (5,3x10x0,6) external-tooth serrated washer.