Bonnell springs vs pocket springs

What a Bonnell unit actually is

Bonnell springs are hourglass-shaped coils, narrow in the middle and wider at each end, joined top and bottom by helical wires that run across the whole unit. It is the oldest mattress spring design still in mass production and it has genuine virtues.

The hourglass shape is progressive: the more you compress it, the more it resists. That is why a Bonnell mattress feels supportive under a heavier person rather than bottoming out, and why the construction persists at the budget end rather than simply being obsolete.

It is also durable. There is a lot of steel, the wire is usually thicker than in a high-count pocket unit, and there is no fabric to wear. A Bonnell mattress on a good base outlasts cheap foam comfortably.

Related terms you will see: open coil is usually used interchangeably with Bonnell, and continuous coil is a different budget construction where rows are formed from a single length of wire. Continuous coil transmits movement along the row even more than Bonnell does.

What a pocket unit does differently

Each spring sits in its own fabric pocket and is not wired to its neighbours. Compress one and the ones beside it barely move.

That produces the two properties pocket springs are bought for. The surface follows the shape of your body rather than responding as a region, so your shoulder can sink while your lumbar stays supported. And on a shared bed, one person turning over does not lift or tip the other side, which is the single most common complaint about older mattresses.

The trade is cost and, at very high counts, individual spring strength.

Spring counts are quoted for a king

This catches almost everyone. A quoted count is for a king size. A double has fewer and a single fewer still, because the density stays roughly constant while the area shrinks.

So a 2,000 pocket mattress in a double does not contain 2,000 springs. Ask for the figure in the size you are actually buying, and compare like with like between brands.

Above about 2,000, the wire gets thinner

This is the trade the premium end never explains, and it runs directly against how high counts are sold.

A king mattress is 150 by 200 centimetres, or three square metres. Fitting 8,000 springs into that means roughly one every 1.7 centimetres in each direction, and units that small cannot be made from thick wire and still compress usefully under a human body.

So a very high count necessarily means thin gauge. What you gain is contouring finer than the body needs and excellent motion isolation. What you lose is individual spring strength, which is exactly what a heavier sleeper depends on.

A well-built 2,000 spring firm mattress supports a heavier body better than a 6,000 spring plush one. More is not better past the point where each spring still does meaningful work.

Micro-springs, and the word hybrid

A third category confuses this further. Micro-springs are small springs in the comfort layer, not the support core, and they sit above something else.

Simba's Aerocoils are 25 millimetres and sit over a foam base. Otty's Original has a 16 centimetre pocket spring core. Both are sold as hybrids, and in the first, foam is what supports you.

So the question that cuts through the marketing: how tall are the springs, and what is underneath them?

Which to buy

Bonnell or open coil is genuinely fine if: you sleep alone, you want a firm surface, and budget is the constraint. It is a sound engineering choice rather than a compromise, and it will outlast cheap foam at the same price.

Pocket springs if: you share a bed, at all. This is not an upgrade in that situation; it is the floor. Also if you sleep on your side, because the shoulder and hip need to sink independently.

And whichever you choose, the base decides how long it lasts. Slats more than about 7.5 centimetres apart cause sagging into the gaps and void most guarantees, which means the frame creates the fault and then disqualifies the claim.

Related reading

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