Product DescriptionBonnell Spring Medium Firm Mattress Double Who needs a Bonnell Spring mattress? The answer is someone who wants a relatively firm and comfortable sleeping surface. And thatís what you get with the Giselle Beddings Bonnell Spring Mattress. Unlike a pocket spring system, a Bonnell spring system uses springs that are hour-glass shaped rather than all of the same diameter. The result is a somewhat firmer mattress than a pocket spring version. The benefits include better support for your body, more resilience and better ventilation. Our Bonnell Spring Mattress delivers all of the above with a level of comfort that surpasses your expectations.