If you have a bent umbrella tube and wish to stiffen the umbrella tube, remove the end cap, cut a Alum 1/4" rod 14" long and put that inside the tube and then put the end cap back on, you could use 1/4" oak round also. If you have a slightly bent tube taper the end a little before you put it in this will help it through the bend. Yes it will add some weight to it but I like the Idea of having a tube that will not break as easily.