bonnelinner spring for compressed mattress Bonnel Spring Series Wire gauge : 1.7mm-2.5mm (14Gauge-12Gauge) Height:8cm-18cm(3inches-7inches) Turns:4 turns-7 turns The bonnel is the common core in making mattress beds and sofa furniture. The firmness of the unit is varied by using different steel wire sizes and numbers of spring. The firmer the bed, the more spring. We use 2 Times of heatreatment to the springs. One time is to heattreat the individual coils prior to assembly of the complete unit wire by helical, the second is to heattreat the whole unit to prevent sagging under load. EWe offers many different bonnel springs with different wire gages in different turns, such as 4-turns, 5-turns, 6-turns. Packing:Welcome your enquires,and we can produce Bonnel spring coils for mattress manufacturing according to your specifications.