Arthur Sleep Cool Rock King Size Mattress
The Arthur Sleep Cool Rock is a pocket spring mattress with a firm sleeping surface, which means noticeably more pushback than a medium feel and better spinal alignment if you sleep on your back or front.
- Extra-firm for back & front sleepers
- Support that follows your shape
- Minimises partner disturbance
£289
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Arthur Sleep Cool Rock Mattress
More available sizes
Last seen for £255 at Mattress Man on 30th October 2026
Mattress details
Mattress
Arthur Sleep Cool Rock Mattress
Size
Firmness
Extra Firm
Construction
Pocket Spring
Depth (cm)
Layers
Layer Details
Key benefits
- 75cm each for two people sharing: That per-sleeper width means you can both settle into your own space without negotiating the middle of the mattress.
- Pocket springs limit partner disturbance: Springs move independently, which means an early riser slipping out at 6am is far less likely to wake the person still asleep.
- Extra length for taller sleepers: At 200cm, the UK king is 10cm longer than the UK Single, welcome if either of you is approaching six foot.
- A firm feel across a wider surface: Extra firm support stays consistent edge to edge, so neither sleeper rolls towards the other during the night.
- Affordable route to a king: The Cool Rock sits at the budget end for pocket springs, so upgrading to the UK king is realistic; compare the prices shown on this page, updated as retailers change them.
This size suits you if...
You share the bed every night and a double has started to feel cramped, especially if one of you keeps different hours and the other is a light sleeper. It also suits taller couples who want the extra length, and back or front sleepers who prefer a firm, no-sink surface with room to spread out. If the dog treats the bed as its own, the extra width absorbs that too.
Consider another size if...
Your bedroom can't take a 150 x 200cm bed comfortably; we suggest allowing at least 2.7m x 2.9m for a UK king. In a tighter room, we'd recommend the UK double instead, which needs around 2.6m x 2.8m.
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FAQ's
Is the Arthur Sleep Cool Rock in a UK king good for couples?
Yes, and arguably better than the smaller sizes. You get 75cm each for two people sharing, and the pocket springs move independently, so one partner shifting or getting up early transfers less movement across the bed. The extra firm surface won't suit lightweight side sleepers, though, so make sure both of you like a firm feel before committing.
Will the Cool Rock UK king fit a new build master bedroom?
Often, but measure first. New build masters can feel smaller than they look once fitted wardrobes go in. We suggest at least 2.7m x 2.9m for a UK king, with more space feeling noticeably more comfortable. If the room falls short, the UK double is 15cm narrower and needs around 2.6m x 2.8m.
Is the UK king Cool Rock long enough for someone over six foot?
At 200cm (5ft x 6ft 6in overall), the UK king gives 10cm more length than the UK Double, which matters more than width if one of you is tall. For anyone approaching or past six foot, that extra length is often the real reason to upgrade rather than the width alone.
Does the firm feel change in the king size?
No, the extra firm feel is the same across every size of the Cool Rock. What changes in the UK king is how the firmness works for two: a firmer surface flexes less when your partner moves, so combined with the independent pocket springs, disturbance across a 150cm width is kept low.
Should we buy the Cool Rock in a UK king or a UK double?
If you share every night, the UK king is 15cm wider and 10cm longer than the UK Double, a difference you feel rather than merely notice. Choose the UK double only if your room is under our suggested 2.7m x 2.9m minimum for a king, or if you rarely share the bed.