It is commonly called concrete reinforcing wire and is available at the big box stores (Lowe's, Home Depot) or else concrete places.

Here is a blog about making them but they refer to the wire as construction wire mesh.

I've been meaning to make me some of the concrete wire mesh (crw)cages for years. I have the wire, so hopefully this will be the year I get at least a few of them made.

hth.

Sue...chemocurl

Here is a link that might be useful: Tomato cages for the serious Gardener

I see by this string that no one is worried about removing them later. I was just thinking after seeing your post wouldn't it be a little easier to bend the four sides and cutting to fit the ends together? They could either be welded or just wired together with a heavy gage wire. I like the wiskey barrel ideal. that would keep it from falling over without cutting the bottom wire which would allow it to be pushed into the ground. If a barrel isn't used you could use chicken wire to retain the soil needed for the raised beds. But then if you don't use the barrels you will also be able to plant around the outer edges of this cage.

It's a bit of work to cut them up into panels, but then they would fold flat for storage. Since I live out in the country I don't worry about my cylinders - just leave 'em out there. move to new location in spring. Just roll one up and secure it, et voila, a tomato cage for the industrial age!

Also since the aren't in a barrel, I have to secure them with a post. Wrapped in plastic they make for easy knock-over, and the tomoato plants can pull them down later in the season.

Here's what I made out of Cattle panels, cut them in sections and bent them in half, strong and last long.

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Here's how I extend them beyond 5ft tall...they act as anchor legs too.

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Be sure to study the pic carefully on where to cut & bend so you don't make any mistakes!