ᐅ Cistern component with unknown function

Dear all, I’m at a loss. I recently purchased a building kit from Siamp, but when I got home, I found that I couldn’t figure out the purpose of one of the components. So I went back to the hardware store, but the salesperson didn’t know what the part was for either.

In the picture below, the part I’m referring to is the one in the top right corner with the two legs. Does anyone know what this is and what it’s used for?

Did you buy that separately, or was it included with the flush tank? In any case, it is the stopper that controls the level of the flush water.

Hello,

the small caps are there to seal the side connection in case the connection comes from the back.
See photo.