Part Identification help please

[Slackline]

I backed the car out of the garage the other day and this was sitting on the garage floor. I don't know what it is or where it came from.

I am sure you guys can recognize it.

mystery part.jpg

[Gregs672000]

Looks like a shock mount rubber donut.

[theunz]

Or a dust cap for a wheel cylinder, although neither could just fall off!

[notoptoy]

Firewall grommet for cables/wires?

[MattC]

Could it have rolled under there from somewhere else?

[DAC21]

Looks like the oil seal boot from the Fuel Pump only bigger. Wish I could find one without having to buy a $50 kit!

[datsun1500]

That really looks like a brake or clutch slave cylinder dust cap, but no clue how they’d come off. Maybe someone dropped it years ago and it finally worked it’s way to freedom.

[Slackline]

I am hoping to get under the car this weekend. I'll check those places.

My firewall grommets seem to be there or have objects through the FW.
Outer diameter is 1 1/4"
ID is just under 3/8.

It would not have come from a 2018 Audi, so it had to originate from the car. Its not from my jack or jack stands.

[Slackline]

The PO said he replaced the clutch slave, so maybe that is it. This could be the old one?

[68DSU]

The PO said he replaced the clutch slave, so maybe that is it. This could be the old one?

Maybe the dust cover?
If it has a hole in the center, and no tear to get it off whatever it was wrapped around, and the car is working, then it almost has to be a left over part.

[JT68]

Really doesn't look familiar. Can you photo the other side?

[datsun1500]

My first feeling was clutch slave dust cover. Here’s a photo of a stock one, I bet if you pull on yours, it’ll look like this

[Linda]

Balljoint boot, leftover part.
Linda

[Slackline]

It is completely flat on the back with just the hole through the (off)center

[datsun1500]

Master cylinder dust cover? Whatever it is, it had to be left somewhere and fell out, no way it came off without being torn