DN of 2-inch punching elbow is 50mm, which is the abbreviation of "DiamètreNominal" in French, indicating the nominal diameter or standard size of pipeline, and the unit is millimeter. However, due to the difference between English and metric systems, the DN values of 2-inch pipes may be slightly different in different standards.

Usually, the DN size corresponding to the 2-inch pipeline standard is about 50-53mm. If it is necessary to determine the DN value of 2-inch punching elbow more accurately, it needs to be further confirmed according to the specific pipe and pipeline standards and manufacturers.