What's this?
 

Found this green thing on my new-to-me 2002 naked.
Something to do with the rear brake fluid.
Any ideas what's going on?

https://i.ibb.co/WHRxHjL/IMG-20210813-182804.jpg

Re: What's this?
 

It replaces the standard brake fluid reservoir

Re: What's this?
 

Thanks. Why would someone do that?

Re: What's this?
 

Cheapskate or racer/wants racing look (it's lighter)

Re: What's this?
 

You normally see that sort of thing where someone's put on rearsets and not thought it through. As Dave says though, probably for the look - you have stock pegs. Or maybe if they've done something with the rear subframe.

Re: What's this?
 

Working on the theory that it may save a few grams in weight!! It will hold enough fluid to do it's job and do away with the really cumbersome and immensely heavy reservoir! If Suzuki thought it was necessary or beneficial they would have fitted them from the factory.

Re: What's this?
 

Its a HRC rear brake reservoir.

Its lighter than OEM and as said is usually fitted to track bikes or those who have modified their bike so that aesthetically the standard reservoir does not fit. I have done this to my GROM when I fitted race rearsets to it.

It holds a smaller amount of liquid than standard, but does not reduce the operation of the brake. The downside to it is that its a little more effort to bleed and the pipe does mist. I understand there is a Suzuki Racing version that is a clear tube that doesn't mist, but I've not got experience of that one myself yet.