1.4 TSI Turbo Coolant pipe O ring or washer

My coolant pipe going to the turbo, has started to leak. But from this and other forums, looks like the parts I need are WHT003366. But I'm confused, is this a metal washer or an O ring ???

I've rang the dealers with the part number and they quoted £7 each.

But can someone confirm the dimensions, I have 10mm int, 2.5mm thickness for a Viton O ring, this item is far cheaper than dealers..

Also, can you offer guidance on how to replace, but looks fairly straight forward.

Thanks in advance