We replaced 11 portholes on our boat with New Found Metals portholes. We love them. They are cast 316 stainless steel. As a matter of fact I have 2 5 x 12 with 1.5” spigots left over. I ordered 11 with 1.5” spigots and 2 needed to be 2” spigots so I have 2 that I want to get rid of.
When I replaced my portholes I had to enlarge the holes in the boat. I used a router with one of NFMs templates. It was a lot of work but the new portholes are awesome.