What are the descriptions of the types of stainless steel pipe fittings?

There are many types of stainless steel pipe fittings, which can be summarized as follows: 1): pipe fittings with variable wall thickness; 2) pipe fittings with variable diameter; 3) pipe fittings for changing sections; 4) bending pipe fittings; 5) expanding pipe fittings; 6): Fittings with crimping and backing; 7): Flanges with flanges and rounded edges.
     1): Pipes with variable wall thickness: means that the wall thickness changes along the length of the pipe;
     2): Variable diameter pipe fittings: the diameter of a pipe end or a part of the pipe is reduced;
     3): Change the pipe fittings of the section: change the circular section into a square, an ellipse, a polygon, etc. as needed;
     4): Bent pipe fittings: The more we contact, the straight pipe is changed into a bend with different radius of curvature, such as elbows, elbows, etc.;
     5): Expanded pipe fittings: Expand the end of the pipe fitting or a certain part to form pipes of various shapes as required;
     6): Fittings with crimping and backing: pipe fittings that increase the overall strength of the pipe end to the outside or inside of the pipe or seal the end of the pipe;
     7): Flange with flange and round edge: the former means that the end of the pipe is convex toward the inside or the outside, and the latter refers to the pipe which forms a bulge or groove in the circumferential direction of the pipe.