Slip-On flanges or SO flanges are commonly lower in price than weld-neck flanges, and to this effect are a popular choice for our customers. It is welded both inside and out to provide suffcient strength and prevent leakage. Slip-On
Pipe Flanges. As made obvious by their name, these pipe flanges slip over the pipe. They're manufactured with an inside diameter that is slightly bigger than the pipe's outside diameter. These attachments are connected to the pipe via fillet weld at the top and bottom of the flange.