Collar is also called stub end is used in place of welded flanges where rotating back up flanges are desired.
Sunny Steel is one of leading and experienced AWWA C207 Flanges Manufacturer in China.
FAQ related to pipe fittings, what are pipe fittings?
A question was put to the PM Engineer (PME) staff (one of SUPPLY HOUSE TIMES sister magazines) asking how nominal pipe size came to be. Here is the answer provided by PME Editorial Director Julius Ballanco.