Old style bolts with a slight dome. Machined from 4142 steel that is heat treated equivalent to Grade 5. The correct style for many vintage vehicles. 

Black Oxide finish

size - 7/16-14x1-1/2 -  A) 1-1/2"  B) 1-1/8"    C) .470    D) 5/8"  - NUT316

size 7/16-14x2              A) 2"         B) 1-1/8"    C) .470    D) 5/8"  - NUT317

size - 7/16-14x2-1/2     A) 2-1/2"  B) 1-5/16"  C) .470   D) 5/8"  - NUT318

size - 7/16-14x3           A) 3"         B) 1-13/16"  C) .470  D) 5/8"  - NUT540