Spring Units

Spring Units

Open Coil

Open coil (also known as Miracoil, Continuous Coil, Standard Coil, Bonnel Coil and Box Spring) are the most common types of mattresses, consisting of an interconnected spring system. 

Coils are measured in gauges which indicate the thickness of the wire used for the springs. The lower the number, the thicker the spring, which typically results in a firmer mattress.  For this reason, many orthopaedic mattresses use an open coil structure.

Pocket Spring

Pocket sprung mattresses are made of a formation of springs that are housed in individual pockets, allowing them to work independently of each other. Pocket sprung mattresses offer high quality support.

Typically, the higher the spring count, the better the support. Spring counts are measured on a 5ft mattress size, and can hold up to 1500 springs in a single layer.


Foam mattresses, including memory and reflex foam, use a different structure. Modified from visco-elastic polyurethane, foam mattresses provide a different feel.



All mattresses have a bordered edge to retain its structure. 

Rod Edge

A Rod Edge is a type of structural edging found around both the top and bottom of the mattress, holding the structure in place. It is used most commonly on open coil structures for frame support, and prevents the mattress from tipping and losing shape. 

Side Stitching

Some mattress borders are stitched on the sides for additional support and to prevent sagging. These can be machine stitched, although hand side stitching is a skilled and traditional technique still used on top quality mattresses. 

Foam Encapsulated

Foam encapsulated borders are used as an alternative to rod edges, foam encapsulated sides are more commonly used on pocket sprung mattresses. 



There is a range of standard mattress sizes in the UK, which include:

  • Small Single 
  • Single
  • Small Double (also called Queen)
  • Standard Double
  • King Size
  • Super King Size

For more detailed information on mattress sizes, see our mattress size guide



Most mattresses consist of a combination of spring units and fillings. A range of materials can be used to fill a mattress, which help determine the overall quality. For a full range of fillings visit our materials page.

Styles & Finishes

Styles & Finishes

Pillow Top

A pillowtop mattress has an extra layer of padding or cushioning attached to the top, to increase comfort. Pillow top mattresses can help those who have back pains by providing a softer sleeping surface.


Tufting involves passing tapes through the mattress at intervals to prevent pocket sprung mattresses losing shape and collapsing.


Quilting produces a smoother and flatter surface when compared with other finishes. This method is mostly used, but not limited to, open coil mattresses.


Handles are stitched to the sides of mattresses for ease of turning, and are often seen on higher-quality mattresses.


Vents are a sign of a quality mattress, embedded in the sides to promote airflow to reduce moisture and heat build-up.

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