I know what I'm looking for, but I don't know what it's called (DIY)
I have cut a round hole in a garden table for an umbrella. I want to finish it off by putting something like this (photo below) in the hole to give it a bit more strength and make it look a bit nicer. These are the same thing one might use to put up shower curtain rail or a clothes rail inside a wardrobe, but if I search for either of those what I find is quite small with a hole half the size I need for my large umbrella. The hole I have cut is 8cm in diameter. I've been searching for "circular bracket". Does anyone know if there's a technical name for one of these things? Thanks.