2"mpt threaded tailpiece 417-5140 for split nut. This is a 2 inch buttress thread to 2 inch male pipe threaded tailpiece. Oring/Gasket available separately: 711-4030 o-ring gasket
2" split compression nut 0121108020 is a heater union split nut with 2 inch buttress thread connections for 2 inch id heaters. Replaces other 2 inch plumbing heater split nuts like