The Bonnell is the classic spring unit, and had, through the years, proven its worth. This spring is hour glass shaped with knotted end rings at top and bottom front sides. A round helical wire connects each single spring along a line either head to toe or side to side. a border wire support goes around the perimeter clipped to each spring on the outer edge of the unit. Springs normally range form 100mm- 170 mm in height with 150mm being the average. 100mm springs are mainly used in sofa beds. The construction of the Bonnell spring unit shows a so-called progressive resiliency: when little weight is applied, the mattress with the tailed springs is softer because the resistance is still low. Then, when more weight is applied, the resistance to the body weight is higher and is increased with the degree of the compression. The number of springs is one of the key quality characteristics.

Bonnell spring units:

are a reasonably priced high quality spring system used in medium quality mattresses

provide excellent support and comfort

3-4 gauges of wire available

the original spring system and still one of the best.