I’m using this bi-folding box spring on an upstairs guest bed. It was much easier to get up the stairs than a traditional queen sized box spring and should work perfectly on a guest bed that gets little use. 
When folded in half it doesn’t seem possible that it will be 5 inches tall but it expands when opened up. It’s too soon to tell how good it is - so far, though, I’m pleased with it. 
I only gave it 4 stars because I’m not sure it would be desirable on a bed that is used daily, even though the design and execution are quite good. I really like the fabric cover that zips closed once opened to the flat position.