Unidentified part

[mikh]

When replacing a water supply line I found a part - it was inserted into the toilet tank where the water line connects to it. Could you please help to identify it - what's the name / purpose (to limit water flow?). Can't find it on any 'toilet parts diagram'. The toilet is quite old, Kohler, there are numbers - 72 - could be the manufacture year.

 

[Mr_David]

put it back. It makes the water spin as it enters the ball cock.
Why?? The engineers got bored when they designed it.

 

[mikh]

Thank you!