Bonell Spring Mattresses The Bonnell spring is the classic Spring Unit, made from round hourglass shaped springs which are tied together to form a mat. A round helical crosswise connects each single spring to a spring unit to provide maximum durability. The Bonnell Spring has continually proven its value over the years with its comfort and durability. The Bonnell Spring is manufactured with the finest ingredients and provides additional comfort necessary for the body whilst offering enough space for free movement and great support.