ANSI B16.5 Class 2500 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 | 133 | 30.2 | 40 | 21.3 | 73 | 15.7 | 88.9 | 7/8 | 4 |
| ¾ | 140 | 31.8 | 43 | 26.7 | 79 | 20.8 | 95.2 | 7/8 | 4 |
| 1 | 159 | 35.1 | 57 | 33.5 | 89 | 26.7 | 108 | 1 | 4 |
| 1¼ | 184 | 38.1 | 73 | 42.2 | 95 | 35.1 | 130 | 1⅛ | 4 |
| 1½ | 203 | 44.4 | 79 | 48.3 | 111 | 40.9 | 146 | 1¼ | 4 |
| 2 | 235 | 50.8 | 95 | 60.5 | 127 | 52.6 | 171.4 | 1¼ | 8 |
| 2½ | 267 | 57.2 | 114 | 73.2 | 143 | 62.7 | 196.8 | 1½ | 8 |
| 3 | 305 | 66.5 | 133 | 88.9 | 168 | 78 | 228.6 | 1⅝ | 8 |
| 4 | 356 | 76.2 | 165 | 114.3 | 190 | 102.4 | 273 | 1⅝ | 8 |
| 5 | 419 | 91.9 | 203 | 141.2 | 229 | 128.3 | 323.8 | 1¾ | 8 |
| 6 | 483 | 108 | 235 | 168.4 | 273 | 154.2 | 368.3 | 2-1/8″ | 8 |
| 8 | 552 | 127 | 305 | 219.2 | 318 | 202.7 | 438.2 | 2-1/4″ | 12 |
| 10 | 673 | 165.1 | 375 | 273 | 419 | 254.5 | 539.8 | 2-5/8″ | 12 |
| 12 | 762 | 184.2 | 441 | 323.8 | 464 | 304.8 | 619.3 | 2-7/8″ | 12 |