This is a 1 inch – 3-quarter inch ozone barb. It is commonly used with 1 inch socket connectors. 3/4 inch vinyl pipe.
Best to use a plumbing cleaner, pipe cement then a metal clip to assemble. You would push the vinyl tube over the top of this.
Commonly called an ozone barb usually because it feeds the ozone jet with an in-line ozone injector added.