A little over a year ago I made the mistake of buying a one-sided innerspring mattress - I had a perfectly fine, firm, double-sided mattress that was 11 years old, and for some reason I thought it was time for a new one.
I bought one of the big “S” brands (on sale) from a major department store, it was described as “firm” - at first, it seemed OK - but about 3 months or so after I got it, it started sagging in the middle - not the required 1 1/2" to be covered under warranty, but enough that I could tell…and enough that it annoyed me. I rotated it as instructed, that didn’t do much - and of course I could not flip it over - also, I quickly discovered it was not nearly firm enough…it was too “bouncy” and soft.
I did some research and found out that this mattress has 15.5 gauge coils - and my research also told me that the thinner the coil, the softer, springier and bouncier the mattress would feel - a thicker gauge coil would feel firmer and more supportive - unfortunately I didn’t do the research until after the fact.
The only way I could get comfortable on this thing was to sleep near the edge, because it had the “foam encased edge” that was very firm, this was the only place on the mattress I could fall asleep, near the edge.
I went to several stores in search of a new mattress - the “mattress store” salesmen all told me the same thing when I asked to see their double-sided mattress: “they don’t make them anymore” - I found out (thankfully) there are lots of mattress manufacturers that still make double-sided, innerspring mattresses.
After a lot of research and shopping - I ordered a Gold Bond Anniversary Firm double-sided mattress from Wayfair and I could not be happier - it’s very firm, double-sided and I am very pleased with the quality - and the price was great! The coils are 12 3/4 gauge - it’s very firm, and comfortable - I now feel like I am on my mattress, not in it - it’s just what I wanted!