We have a sofa bed for guests and I've hated having guests sleep on its mattress. It was 10 years old and I figured it couldn't be too great having been folded up for YEARS. The new mattress did get rave reviews from my most recent guest (who on a previous trip elected couch sleep over sofa bed). It IS comfortable, however it is NOT 4.5 inches. Maybe 4 inches. This has been a VAST improvement over the previous mattress. Would definitely purchase again and/or recommend to others.