Here's a pic of the frame: https://i.imgur.com/BViZJri.jpg
The bottom rectangle is 12" x 24", and then the top/side pipes are 36" each.
It's a bunch of steel pipe from Home Depot, and sturdy enough you could do pullups on it. The pipe isn't super cheap, was around $200 total I think. I went with 1 inch diameter because it would hold the monitor arms better, but you could go thinner and cheaper with a different monitor mounting solution.