Mattresses are complicated enough, finding the right mattress can be really tough and even after you've decided on the spring system, base layer, comfort layer and materials, you then have a magnitude of differently named products all reflecting slight inconsistences. What Bensons for Beds have started doing which I personally really like, is they simply provide the mattress in different tensions, that way, you find the product with the correct specification, and then select the most suitable tension. You really cannot go wrong.