Spring King Ruby Ortho Extra Firm King Size Mattress
The Spring King Ruby Ortho Extra Firm is an orthopaedic open coil mattress at the firmest end of the scale.
- Extra-firm for back & front sleepers
- Even support with less sinking
- Breathable cover helps you stay cool
£319
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Spring King Ruby Ortho Extra Firm Mattress
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Mattress details
Mattress
Spring King Ruby Ortho Extra Firm Mattress
Size
Firmness
Extra Firm
Construction
Orthopaedic
Open Coil Spring
Depth (cm)
27
Layers
3
Layer Details
Cover
A breathable Belgian damask fabric cover. The breathability helps air move away from your body, which means you are less likely to overheat.
Comfort Fillings
Soft white fibre fillings made from 100% polyester. These add a little softness over the springs, though the overall feel remains extra firm.
Support System
A traditional open coil unit built from one continuous high tensile spring formed into a lattice. This spreads support evenly across the mattress, which means a stable, uniformly firm surface underneath you.
Layer details from mattressnextday.co.uk product page, September 2026.
Key benefits
- More room each: At 75cm per person, the UK king gives you 7.5cm more each than the UK double, which means fewer nudged elbows when one of you turns over.
- Extra length for taller sleepers: At 200cm, the UK king is 10cm longer than the UK double, so a taller partner can lie straight on the firm surface without their feet reaching the end.
- A little distance from an early riser: The extra width puts slightly more space between you when one partner gets up hours before the other, although the continuous coil still carries some of that movement across.
- Even firmness edge to edge: The single continuous spring lattice runs the full 150cm width, which means neither side of the bed ends up feeling softer than the other.
- Easier to fit than a super king: We suggest at least 2.7m x 2.9m for the UK king, a smaller footprint than the 3m x 2.9m we suggest for the UK super king.
This size suits you if...
You share the bed with someone and you both sleep on your back or front and want a hard surface, one of you is tall enough to find a 190cm bed short, or your bedroom comfortably clears our suggested minimum of 2.7m x 2.9m.
Consider another size if...
Your bedroom falls short of our suggested 2.7m x 2.9m once the wardrobes are in. We'd recommend the UK double instead, for which we suggest at least 2.6m x 2.8m.
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FAQ's
Is the Spring King Ruby Ortho UK king big enough for two people?
Yes, for most couples. The UK king gives each of you 75cm of width, compared with 67.5cm each on the UK double, so you gain 7.5cm apiece. If you both sprawl, the UK super king gives 90cm each, which is 15cm more per person than the UK king.
Will I feel my partner move on a Ruby Ortho UK king?
Probably, yes, a little. The open coil is made from one continuous spring, so movement travels across the whole surface. The UK king's extra width over the UK double puts more space between you, which helps if one of you rises early, but light sleepers may prefer a pocket sprung mattress.
Is the Spring King Ruby Ortho king size long enough for a tall person?
The UK king is 200cm long (6ft 6in), which is 10cm longer than the UK double, the UK small double and the UK single. That extra length is often the real reason taller couples size up. The UK super king is the same length, so going bigger only adds width.
Will a Ruby Ortho UK king fit in a new build master bedroom?
Measure after the wardrobes and bedside tables are in, as new build rooms often shrink once furnished. We suggest at least 2.7m x 2.9m for the UK king, with 3.2m x 3.2m giving comfortable space to walk around. The mattress itself measures 150 x 200cm, or 5ft x 6ft 6in.
Should we get the Ruby Ortho in a UK king or a UK super king?
Choose the UK king if you want more room than a UK double without giving up floor space. The UK super king is 30cm wider for 90cm each, but we suggest at least 3m x 2.9m for it. Both are 200cm long, so a taller partner is equally well served by either.