Our bolts are manufactured to comply to DIN Standard 931 / A2 304 and A4 316. Supacheap Bolts currently stock M6, M8, M10, M12, M16 and M20 diameter bolts up to 160mm in certain diameters in Fresh Water Grade 304 and Marine Grade 316. Please note : Our Image is of a generic standard bolt and thread lengths vary slightly per size so check with us before ordering if this dimension is of importance. Typically, thread lengths for our hex bolts will be to the recognised international metric standard. All bolt lengths are measured from under the head.