ANSI B16.5 Class 300 Welding Neck Flanges
| Nominal Pipe Size | Outside Diameter (O) | Thickness (T) | Raised Face Diameter (R) | Length Thru Hub (Y) | Point of Weld (A) | Hub Diameter (X) | Bore (B) | Approximate Weight | Bolt Circle (C) | Number of Holes | Diameter of Holes |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2 | 3.75 mm | 0.56 mm | 1.38 mm | 2.06 mm | 0.84 mm | 1.50 mm | 0.62 mm | 2 lb | 2.63 mm | 4 | 0.63 mm |
| 3/4 | 4.63 mm | 0.63 mm | 1.69 mm | 2.25 mm | 1.05 mm | 1.88 mm | 0.82 mm | 3 lb | 3.25 mm | 4 | 0.75 mm |
| 1 | 4.88 mm | 0.69 mm | 2.00 mm | 2.44 mm | 1.32 mm | 2.13 mm | 1.05 mm | 4 lb | 3.50 mm | 4 | 0.75 mm |
| 1 1/4 | 5.25 mm | 0.75 mm | 2.50 mm | 2.56 mm | 1.66 mm | 2.50 mm | 1.38 mm | 5 lb | 3.88 mm | 4 | 0.75 mm |
| 1 1/2 | 6.13 mm | 0.81 mm | 2.88 mm | 2.69 mm | 1.90 mm | 2.75 mm | 1.61 mm | 7 lb | 4.50 mm | 4 | 0.88 mm |
| 2 | 6.50 mm | 0.88 mm | 3.63 mm | 2.75 mm | 2.38 mm | 3.31 mm | 2.07 mm | 9 lb | 5.00 mm | 8 | 0.75 mm |
| 2 1/2 | 7.50 mm | 1.00 mm | 4.13 mm | 3.00 mm | 2.88 mm | 3.94 mm | 2.47 mm | 12 lb | 5.88 mm | 8 | 0.88 mm |
| 3 | 8.25 mm | 1.13 mm | 5.00 mm | 3.13 mm | 3.50 mm | 4.63 mm | 3.07 mm | 15 lb | 6.63 mm | 8 | 0.88 mm |
| 3 1/2 | 9.00 mm | 1.19 mm | 5.50 mm | 3.19 mm | 4.00 mm | 5.25 mm | 3.55 mm | 18 lb | 7.25 mm | 8 | 0.88 mm |
| 4 | 10.00 mm | 1.25 mm | 6.19 mm | 3.38 mm | 4.50 mm | 5.75 mm | 4.03 mm | 25 lb | 7.88 mm | 8 | 0.88 mm |
| 5 | 11.00 mm | 1.38 mm | 7.31 mm | 3.88 mm | 5.56 mm | 7.00 mm | 5.05 mm | 32 lb | 9.25 mm | 8 | 0.88 mm |
| 6 | 12.50 mm | 1.44 mm | 8.50 mm | 3.88 mm | 6.63 mm | 8.13 mm | 6.07 mm | 42 lb | 10.63 mm | 12 | 0.88 mm |
| 8 | 15.00 mm | 1.63 mm | 10.63 mm | 4.38 mm | 8.63 mm | 10.25 mm | 7.98 mm | 67 lb | 13.00 mm | 12 | 1.00 mm |
| 10 | 17.50 mm | 1.88 mm | 12.75 mm | 4.63 mm | 10.75 mm | 12.63 mm | 10.02 mm | 91 lb | 15.25 mm | 16 | 1.13 mm |
| 12 | 20.50 mm | 2.00 mm | 15.00 mm | 5.13 mm | 12.75 mm | 14.75 mm | 12.00 mm | 140 lb | 17.75 mm | 16 | 1.25 mm |
| 14 | 23.00 mm | 2.13 mm | 16.25 mm | 5.63 mm | 14.00 mm | 16.75 mm | 13.25 mm | 180 lb | 20.25 mm | 20 | 1.25 mm |
| 16 | 25.50 mm | 2.25 mm | 18.50 mm | 5.75 mm | 16.00 mm | 19.00 mm | 15.25 mm | 250 lb | 22.50 mm | 20 | 1.38 mm |
| 18 | 28.00 mm | 2.38 mm | 21.00 mm | 6.25 mm | 18.00 mm | 21.00 mm | 17.25 mm | 320 lb | 24.75 mm | 24 | 1.38 mm |
| 20 | 30.50 mm | 2.50 mm | 23.00 mm | 6.38 mm | 20.00 mm | 23.13 mm | 19.25 mm | 400 lb | 27.00 mm | 24 | 1.38 mm |
| 22 | 33.00 mm | 2.63 mm | 25.25 mm | 6.50 mm | 22.00 mm | 25.25 mm | 21.25 mm | 465 lb | 29.25 mm | 24 | 1.63 mm |
| 24 | 36.00 mm | 2.75 mm | 27.25 mm | 6.63 mm | 24.00 mm | 27.63 mm | 23.25 mm | 580 lb | 32.00 mm | 24 | 1.63 mm |