Mattress Online Rock Hard Ultra Firm Mattress
The Rock Hard Ultra Firm from Mattress Online is an all-foam orthopaedic mattress rated extra firm, which means very little sink and a sleeping surface that keeps you on top of the bed rather than in it.
- Very firm, no sinking feel
- Moulds to ease pressure points
- 100-night trial
£279
Get the lowest price we've found
At 25cm deep, the Rock Hard Ultra Firm combines reflex foam with ortho PU foam to hold your spine in line, and it comes with a 100-night trial and a 3-year guarantee. It's available in five UK sizes at a price that's good value for a specialist firm mattress. It suits back sleepers and anyone who has found softer mattresses leave them aching, although lightweight side sleepers will almost certainly find it too unyielding.
Mattress specifications
Firmness
Firm
Type
Orthopaedic
Depth (cm)
25
Number of Layers
3
Trial Period (nights)
100
Warranty (years)
3
Price Range
£279 to £529
Best Sleeping Position(s)
Back Sleeping
Stomach Sleeping
Certifications
BS 7177
Assessed from Mattress Online's published specification for this mattress, captured September 2026, and from regular price comparison across our UK retail partners.
Why should you choose this mattress?
If you genuinely want a very firm bed, this mattress does exactly what its name promises. The ortho PU foam core adds firm support while still moulding to your shape, which means pressure relief without the soft, sinking feel that aggravates some backs. It's handcrafted in the UK, conforms to BS7177: 2008 for home use, and comes from a National Bed Federation Approved Brand. The 100-night trial matters here more than usual: extra firm mattresses divide opinion, and being able to try it at home takes the risk out of the decision. Free delivery to most locations, with next day weekday delivery available, rounds things off nicely.
Key features & layer details
Reflex Foam
A flexible reflex foam layer sits at the top, which means responsive support that helps keep your spine aligned. It has a little give, but this is not a plush comfort layer.
Ortho PU Foam
The ortho PU foam core provides the extra-firm support this mattress is built around. It moulds to your shape to reduce pressure points and encourage better posture.
Reflex Foam
A second reflex foam layer at the base promotes spinal alignment from underneath. It moulds slightly to your body for a more personalised feel.
Layer details from mattressonline.co.uk product page, September 2026.
Best suited for?
Back sleepers
The ortho PU foam core gives extra-firm support under the spine, which means your back stays level without sinking into the mattress.
Budget buyers
The copy describes it as good value for a specialist firm mattress, so you get a very firm all-foam build without paying specialist prices.
Heavier sleepers
A 25cm build with a firm ortho PU foam core resists sinking, which means heavier bodies stay supported rather than dipping through the layers.
Combination sleepers
Responsive reflex foam on top has a little give, which means changing position feels easy, though the surface stays firm throughout.
This is not the mattress for side sleepers, especially lighter ones, who need enough give at the shoulder and hip to keep the spine level. Anyone who likes a cushioned, cradling feel should look elsewhere too. And if you want springs rather than an all-foam build, this won't suit.
Save on an earlier or ex-display model
Some retailers still sell the earlier version of this mattress, or ex-display and returned stock at a lower price. These are the sizes where it costs less than the current model's best price.
Mattress Online Rock Hard Ultra Firm Mattress
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FAQ's
How firm is the Rock Hard Ultra Firm mattress?
Mattress Online rates it extra firm, and owner reviews back that up, describing an extremely firm sleeping experience. Expect minimal sink and a very supportive surface. If you're used to a medium mattress, this will feel like a significant step up in firmness.
Does the Rock Hard Ultra Firm mattress have springs?
No, it's an all-foam mattress. The 25cm build uses layers of reflex foam and ortho PU foam, which together provide firm orthopaedic support without any spring unit.
Is there a trial period on the Rock Hard Ultra Firm mattress?
Yes, Mattress Online offers a 100-night trial, so you can sleep on it at home before committing. It also comes with a 3-year guarantee. Given how divisive extra firm mattresses can be, that trial is genuinely useful.
How much does the Rock Hard Ultra Firm mattress cost?
It depends on the size you choose, and the price table on this page shows the current price for each size. It's available in five sizes: UK Single, Small Double, Double, King and Super King.
What delivery options does Mattress Online offer?
Delivery is free to most locations, with next day delivery available on weekdays and weekend delivery as an option. Delivery to your room of choice and old mattress removal are available for an extra charge.
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