Metric Coarse threaded ( M8 x 1.25mm ) High Tensile Grade 10 Flanged Self Locking All Metal Hex Nuts with great corrosion resistence due to the ultra high performing Geomet 720 Black Zinc Flake Coating. 
DIN 6927 
Spanner Size 13mm
This version has been Stamped in the manufacturing process, some are pinched to achieve the same locking capability.
These are the preferred coatings for fasteners and other parts in the automotive industry, as they offer various advantages:
Good appearance (colouring)
Very good protection against corrosion (500-1000 hours with a required duration of salt spray in the case of our products)
Resistant to extreme temperatures
Excellent chemical resistance
Environmentally friendly
Excellent friction characteristics
No warm-loosening torque
No risk for high-strength fasteners of any hydrogen embrittlement
Electric conductivity