The plain flange, also known as plate flange, flat flange, or plate slip on flange, is a kind of slip on flange without a hub. It has a simple structure, looking like a flat circular disk. There is an inner bore in the middle for the pipe to pass through, and several bolt holes evenly distributed around the perimeter. This design enables it to be easily welded onto the end of a steel pipe and then bolted to another pipe or relevant equipment.