toilet syphone?

Hi
I have a ideal standard duelflush once working out how to remove lid, I fond the syphone, Having been given a seal from my local plumb center which i was told is the cause off it trickling into the pan, it does not look like the one i was shown in the plumbing shop.
The ones shown where a twist and lock type, the one in mycistern as a strap on either side with small squires in look like they clip over these to old in place
i need to remove top section to replace washer and presumably will with draw from bottom section to do this job. thank you anybody who cn help me