What is this adjuster in the shifting cable? In the shifting housing leading to my Shimano R7000 Front Derailleur sits an adjuster (see attached image). I could not find any documentation on the Shimano Website. Does anybody know (1) what this is, and (2) when to use it? ![cylindric adjuster in shifting cable](

It is an inline barrel adjuster. By holding the end closest to the Shimano "O" and rotating the knurled end you can finely adjust the shift point of the front derailleur. If looking at it from the knurled end, counterclockwise rotation will make the adjuster longer.Clockwise rotation will make the adjuster shorter. This movement will increase or decrease cable tension.