It is extension of 20mm.
I tear off the painting of the part welding.
Then, I cut it.
I weld a pipe of L=20mm.
In most cases, even genuine parts use the pipe of the standard. Therefore the pipe of the just same diameter is available.
I used an electric-resistance weld pipe of STKM.
I point-weld it as straight.
If it beats it with a hammer lightly after having welded one place and revises it, it goes well.
I was able to do it straight.