This is a 1-1/2" Triclover (TC) to 1" NPS female thread adapter. Note that 1" NPS is the most common thread type on water heater elements. The flange measures 2" diameter actual. 304 SS. While we prefer the use of the Hot Pod ETC product for adapting threaded elements to TC, many customers ask for this stand alone adapter so here it is. Note that an oring or gasket seal between the element and adapter is common, you can also get a seal using teflon tape if desired.