ANSI B16.5 Class 300 Welding Neck Flanges
| NPS | Outside Diameter (O) | Thickness (T) | Hub Diameter (X) | Neck Diameter (A) | Length Through Hub (Y) | Bore (B) | Diameter of Bolt Circle (C) | Diameter of Bolt Holes (in) | Number of Bolts |
|---|---|---|---|---|---|---|---|---|---|
| ½ | 95 | 12.7 | 38 | 21.3 | 51 | 15.7 | 66.5 | 5/8 | 4 |
| ¾ | 117 | 14.2 | 48 | 26.7 | 56 | 20.8 | 82.6 | 3/4 | 4 |
| 1 | 124 | 15.7 | 54 | 33.5 | 60 | 26.7 | 88.9 | 3/4 | 4 |
| 1¼ | 133 | 17.5 | 64 | 42.2 | 64 | 35.1 | 98.6 | 3/4 | 4 |
| 1½ | 155 | 19 | 70 | 48.3 | 67 | 40.9 | 114.3 | 7/8 | 4 |
| 2 | 165 | 20.6 | 84 | 60.5 | 68 | 52.6 | 127 | 3/4 | 8 |
| 2½ | 190 | 23.9 | 100 | 73.2 | 75 | 62.7 | 149.4 | 7/8 | 8 |
| 3 | 210 | 26.9 | 117 | 88.9 | 78 | 78 | 168.1 | 7/8 | 8 |
| 3½ | 229 | 28.4 | 133 | 101.6 | 80 | 90.2 | 184.2 | 7/8 | 8 |
| 4 | 254 | 30.2 | 146 | 114.3 | 84 | 102.4 | 200.2 | 7/8 | 8 |
| 5 | 279 | 33.3 | 178 | 141.2 | 97 | 128.3 | 235 | 7/8 | 8 |
| 6 | 318 | 35.1 | 206 | 168.4 | 97 | 154.2 | 269.7 | 7/8 | 12 |
| 8 | 381 | 39.6 | 260 | 219.2 | 110 | 202.7 | 330.2 | 1 | 12 |
| 10 | 444 | 46 | 321 | 273 | 116 | 254.5 | 387.4 | 1⅛ | 16 |
| 12 | 521 | 49.3 | 375 | 323.8 | 129 | 304.8 | 450.8 | 1¼ | 16 |
| 14 | 584 | 52.3 | 425 | 355.6 | 141 | 336.54 | 514.4 | 1¼ | 20 |
| 16 | 648 | 55.6 | 483 | 406.4 | 145 | 387.34 | 571.5 | 1⅜ | 20 |
| 18 | 711 | 58.7 | 533 | 457.2 | 157 | 437.94 | 628.6 | 1⅜ | 24 |
| 20 | 775 | 62 | 587 | 508 | 161 | 488.94 | 685.8 | 1⅜ | 24 |
| 22 | 838 | 65 | 641 | 558.8 | 164 | 539.94 | 743 | 1⅝ | 24 |
| 24 | 914 | 68.3 | 702 | 609.6 | 167 | 590.94 | 812.8 | 1⅝ | 24 |