Please identify the unusual plastic washer

[PedalCat]

It's from my kitchen sink waste

 

[PedalCat]

 

[PedalCat]

The second photo is the right way up, so to speak. It has a kind of C section shape and thereby kind of wraps over the pipe. Pardon the multiple posts, doing this on a smartphone is clunky.

 

[ebikeerwidnes]

Try taking it to a proper plumber's merchant's - they might be able to identify it?

 

[Ming the Merciless]

Looks like a normal oring washer that has split due to age.

 

[classic33]

About 13/4"(pipe diameter) across?

Sealing washer on the underside of the sink.

 

[sleuthey]

To me it looks like the seal that joins the bottom of the waste to the top of the trap. Bottom right in both below.

Edit: PS the C shape you describe is normally due to the thickness of the waste male thread being thinner than the seal itself thus causing an imprint.