Triclover. Triclamp. Sanitary. TC. These are all the names you'll hear people using to refer to these industry standard connection parts. What you need to know: This is a flange to flange connection system that sandwiches a gasket in between. The gasket provides the seal and also indexes the flanges together so they stay lined up (via a groove in the flange and a protrusion in the gasket). A split band clamp holds the flanges together and is usually secured via a single wingnut. The size naming refers to the OD of the piping the flange is typically welded to and sometimes that is quite counterintuitive. 1/2" and 3/4" TC share the same 1" flange diameter. 1" and 1.5" share the same 2" flange diameter. From there, every TC size has a flange about 1/2" larger than it's name.
There are hundreds of TC parts listed here. Feel free to browse through them all if you like (note that the numbers at the bottom right of the page indicate that there are more pages) or you can select one of the subcategories of TC sizes below to narrow the products down by size.