My neighbour used this product instead of concrete to set his fence posts several years ago. The 25' long, 6' high fence is still straight and solid. So I thought I'd try it on a couple of posts that needed replacing in my yard. The package advertises that one pack can do two 4x4 posts. In theory. I mixed the two parts together for the suggested 20 seconds and the bag got hot and swelled up so when I opened the corner it streamed out like a shook up beer. All over the ground and trees and plants. I managed to get enough in post hole only. I got a second package for the remaining post and it worked out great. I didn't mix it as long and as soon as the pack started getting warm I cut the corner and poured it in to the hole. It was too much and I had to trim the mushroom off so to speak. Seems like a good substitute to concrete. Same or less price. Lots less work. Sets in a 1/2 hour. Your posts have to be set exactly as you want them because there is literally only a few seconds before the foam starts to set and adjusting the post becomes impossible without ruining the foam.