DIN 7990 - Hexagon Head Bolts with Hexagon Nut for Steel Structures Standard Dimensions and Specifications Click the Button to Download DIN 7990 – Hexagon Head Bolts with Hexagon Nut for Steel Structures Standard Dimensions and Specifications in PDF Format DIN 7990 PDF Steel: 4.8, 5.8, 8.8, 10.9, 12.9Stainless: A2,A4 Terminology and Measurements d – The Nominal Diameter of the Threadl – Length of Bolts – Size Hex Head Turnkeyb – Length of the Threadk – Head Heighte – The Diameter of the Circumscribed Circle