Firmness
Firm
Type
Orthopaedic
Depth (cm)
25
Number of Layers
3
Trial Period (nights)
100
Warranty (years)
3
Price Range
£269 to £529
Best Sleeping Position(s)
Certifications
Assessed from Mattress Online's published specification for this mattress, captured September 2026, and from regular price comparison across our UK retail partners.
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 & what's inside
- 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.
Who's it NOT for?
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.
Mattress Online Rock Hard Ultra Firm Mattress
View all mattresses
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?
Prices range from £269 to £529 depending on size, starting from £269 for a UK Single. 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 costs £20.00, and old mattress removal is available for £35.00.
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