And in fairness to Jason, if you ask an expert you'll get an expert answer.
The sets of fibre sealing washers on ebay just now are not tap washers, they are sealing washers to seal the thread at the back of the tap where it screws into it's mating pipe. That ebay brings them to the screen when the search string contains the words tap and washer is down to the shortcomings of eBay's search engine, not Jason's expertise.
A tap washer, on the other hand, lives inside a tap and is screwed down onto the tap seat by the operating handle and thereby block the flow of water through the tap. It sits on a jumper which guides it onto its seat and stops it distorting under the forces exerted on it by the water pressure.
One hopes that the OP meant what he said when he asked for a tap washer. His description of same corroborates the terminology he has used.
And you are absolutely right, there is no need for silly remarks.
Edited By Simon Williams 3 on 06/03/2018 20:42:25