Cold punched boron steel. ISO strength 8. zinc plated - layer thickness 12μ. Stainless steel cap on nut. Made in Italy. Long ring spanner for tightening the nut: 17 mm length 70 mm 82370. 19 mm length 70 mm 82364. 21 mm length 70 mm 82365. 17/19 mm length 38 mm 39264V.