Danco 36561W Basin Mack Gasket 2' OD x 1-1/4 " ID  x 3/8 " Thick, 10 per Bag Durable rubber construction 2 in. O.D. X 1-1/4 in. I.D. X 3/8 in. Thick Used as a seat between the PO Plug and sink Basin Easy to install Bag of 1 gaskets