width across flats s , in mm limit deviation, in mm mass per unit length M , in kg/m cross-sectional area A , in cm^2 13 ±0.4 1.15 1.46 14 ±0.4 1.33 1.70 15 ±0.4 1.53 1.95 16 ±0.5 1.74 2.22 17 ±0.5 1.96 2.50 18 ±0.5 2.20 2.81 19 ±0.5 2.46 3.13 20.5 ±0.5 2.86 3.64 22.5 ±0.5 3.44 4.38 23.5 ±0.5 3.75 4.78 25.5 ±0.6 4.42 5.63 28.5 ±0.6 5.52 7.03 31.5 ±0.6 6.75 8.59 33.5 ±0.6 7.63 9.72 35.5 ±0.8 8.56 10.9 37.5 ±0.8 9.56 12.2 39.5 ±0.8 10.6 13.5 42.5 ±0.8 12.3 15.6 47.5 ±0.8 15.3 19.5 52 ±1 18.4 23.4 57 ±1 22.1 28.1 62 ±1 26.1 33.3 67 ±1 30.5 38.9 72 ±1 35.2 44.9 78 ±1 41.4 52.7 83 ±1.3 46.8 59.7 88 ±1.3 52.6 67.1 93 ±1.3 58.8 74.9 98 ±1.3 65.3 83.2 103 ±1.5 72.1 91.9