mystierious hole

[trx400EXtreme]

Just wanting to know if you guys know what this is. there is a little hole on the right hand side on plastics right by your leg. my cousin has one and we are both wanting to know what it is.
thanx.

[jonboy]

It is for checking the rear brake fluid level. if you shine a flashlight in it you can see the level a lot better.

[trx400EXtreme]

thanx