3/4'' (inside diameter) for 3/4''weathervane rods,,brass retaining hook .THE hook SERVES THE PURPOSE OF keeping the large weathervane top figure from flying off the rod.It also can be used on a 3/4'' bottom rod with a 1/2'' top rod for larger weathervanes for THE SAME purpose.FOR INFORMATIONAL PURPOSES, THIS HOOK IS USUALLY USED FOR THINGS THAT CREATE LIFT,,, LIKE,,, DUCKS,HERONS,PLANES,EAGLES,ECT.SHIPS FAST !!!

PLEASE NOTE THIS IS NOT A CHEAP PART,WILL LAST FOR YEARS AND YEARS,,,,,,AND WILL NOT RUST,,,BUYER BEWARE!!!!! DO YOU REALLY WANT TO PAY FOR SOMEONE TO FIX YOUR WEATHERVANE AGAIN IN A FEW YEARS,,,??? THEN BUY ALUMINUM !!! 24 HOUR SHIPPING IN MOST CASES.