ANSI B16.5 Class 900 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 | 14.2 | 38 | 21.3 | 60 | 15.7 | 66.5 | 5/8 | 4 |
| ¾ | 117 | 15.7 | 48 | 26.7 | 70 | 20.8 | 82.6 | 3/4 | 4 |
| 1 | 124 | 17.5 | 54 | 33.5 | 73 | 26.7 | 88.9 | 3/4 | 4 |
| 1¼ | 133 | 20.6 | 64 | 42.2 | 73 | 35.1 | 98.6 | 3/4 | 4 |
| 1½ | 155 | 22.4 | 70 | 48.3 | 83 | 40.9 | 114.3 | 7/8 | 4 |
| 2 | 165 | 25.4 | 84 | 60.5 | 102 | 52.6 | 127 | 3/4 | 8 |
| 2½ | 190 | 28.4 | 100 | 73.2 | 105 | 62.7 | 149.4 | 7/8 | 8 |
| 3 | 241 | 38.1 | 127 | 88.9 | 102 | 78 | 190.5 | 1 | 8 |
| 4 | 292 | 44.5 | 159 | 114.3 | 114 | 102.4 | 235 | 1¼ | 8 |
| 5 | 349 | 50.8 | 190 | 141.2 | 127 | 128.3 | 279.4 | 1⅜ | 8 |
| 6 | 381 | 55.6 | 235 | 168.4 | 140 | 154.2 | 317.5 | 1¼ | 12 |
| 8 | 470 | 63.5 | 298 | 219.2 | 162 | 202.7 | 393.7 | 1½ | 12 |
| 10 | 546 | 69.8 | 368 | 273 | 184 | 254.5 | 469.9 | 1½ | 16 |
| 12 | 610 | 79.2 | 419 | 323.8 | 200 | 304.8 | 533.4 | 1½ | 20 |
| 14 | 641 | 85.9 | 451 | 355.6 | 213 | 336.54 | 558.8 | 1⅝ | 20 |
| 16 | 705 | 88.9 | 508 | 406.4 | 216 | 387.34 | 616 | 1¾ | 20 |
| 18 | 787 | 101.6 | 565 | 457.2 | 229 | 437.94 | 685.8 | 2 | 20 |
| 20 | 857 | 108 | 622 | 508 | 248 | 488.94 | 749.3 | 2-1/8″ | 20 |
| 24 | 1041 | 139.7 | 749 | 609.6 | 292 | 590.94 | 901.7 | 2-5/8″ | 20 |