​Specifies requirements for single-nut and double-nut type steel tower bolts, including step bolts, with ISO metric coarse pitch series threads, in diameters from 12 mm to 30 mm, and lengths from 35 mm to 160 mm, suitable for use in electricity transmission towers and similar structures. Also includes requirements for nuts and washers. Diameter/length code marking, clamping lengths, and derivation of length tolerances are covered in appendices.