Quality material: ASTM A 193 B16 or Durehete 950 or BS1506: 671-B16. Bolt length without the head, this means the shaft length: 40 mm 100 to 200 pieces 45 mm 200 to 400 pieces 50 mm 100 to 200 pieces 55 mm 200 to 400 pieces 70 mm 100 to 200 pieces Thread length on each bolt, 35 mm Thread type M12, pitch 1.75. Thread tolerance to BS 3643 Part 2 medium class 6g Head dimensions 18.95 to 19 mm max. for wrench size 19 mm Head height 8 mm Nickel coating all bolts to BS 3382 part 3