Brake master cylinder question
 

1990 1.6D Jetta.
Just bought new brake master cylinder. I noticed after installation that the old master cylinder had a small black plunger like piece that was located inside one of the two holes into which the reservoir is mounted. What is the purpose of this piece? Is it to keep foreign material from entering the fluid passageways during shipping? Or is it necessary for proper functioning of the master cylinder.
Thanks

Tim
New at this

Welcome to the forum Tim. Attachment 2693

I'm not sure what you mean can you post a picture?

https://volkswagenforum.com/forum/ne...gnature-34185/