So I flushed my Clutch Master, and I noticed this plastic piece in the reservoir.

What is it?

 

Everyone's got it.
I think its purpose is to seal the system in case the reservoir runs empty.
Let's see what our gurus have to say

 

I did a quick Google search and found this:

http://www.cb7tuner.com/vbb/showthread.php?t=46080

 

yeah i think we all should have it. my integra and civic both have it

 

It keeps air from getting in the lines when the fluid runs low, and it might just be the picture but your fluid looks very dark, what did you use.

 

Thanks for the replies guys, that is an ingenious idea!

The picture makes the fluid look darker than it actually is. I flushed it with Honda Dot 3 and there was a huge decrease in pedal effort. If anybody is contemplating a Clutch fluid flush, do it. The bottom of my reservoir had a dark film on it so make sure you use a turkey baster to remove the fluid and wipe the reservoir clean.