Outsunny Outdoor Universal Cross Brace Stand for Small Offset Umbrella or Large Market Umbrella, Cross Umbrella Base for Patio Umbrella, Black

I had this happen to me last year. I had previously purchased two different kinds of cantilever umbrellas at different times. When the bases needed to be replaced, I found that each umbrella had a differently shaped crossbar. One was shaped like a "plus sign" and would perfectly fit a square base. The other one was shaped more like a cross and would fit a rectangular base. I looked through pictures of bases on Amazon and matched the shape of the bases to the shape of the crossbars I had. Finally found some matches. Here are a couple of links to see what I am talking about. I am not recommending the products in these links. They are just for visual purposes. Hope this helps Plus Sign Shaped Cross Shaped