Harley Davidson Knucklehead. Part # 60546-37 Inner Primary Drain Tube Kit. .
This is a kit that fits on the inside primary. The nipple is silver soldered to the lower back of the primary and the tube and nut mount to that.
Almost all after market primaries do not have this correct primary drain.
Fits Harley Davidson Big Twins. All Models from 1937 to 1957
Includes tube, nipple, and nut (see picture)