Firmness
Firm
Type
Orthopaedic
Depth (cm)
23
Number of Layers
Trial Period (nights)
100
Warranty (years)
10
Price Range
£254 to £588
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.
This is a mattress for people who know they want a very firm bed, perhaps on medical advice or simply from experience. The reflex foam moulds to your body to promote spinal alignment, which means support where you need it without the softness that some backs can't tolerate. At 23cm deep it's a proper full-height mattress, not a budget slab. The 100-night trial gives you a full season to be sure, and the 10-year guarantee is reassuring at this price. Delivery is free to most locations, with next-day weekday delivery, a two-hour time slot and the option of room-of-choice delivery for £20.00. Old mattress recycling is available for £35.00, which takes one chore off your list.
Key Features & what's inside
- Reflex Foam. A supportive foam that moulds to your body, which means it promotes spinal alignment and a slightly personalised feel despite the very firm surface. It's durable and resilient, holding its shape for an extended period of time.
Layer details from mattressonline.co.uk product page, September 2026.
Who's it NOT for?
If you like a bed with any give, look elsewhere: this is the brand's firmest rating and owners describe it as feeling like a solid surface. Lightweight sleepers and dedicated side sleepers will likely find it too unyielding at the shoulder and hip. Its substantial weight also makes rotating it a two-person job.
Mattress Online Rock Hard Super Firm Foam Mattress
Across 361 reviews on the Mattress Online product page, rated 4.7, owners consistently describe a very firm, supportive feel that alleviates back pain, with several likening it to sleeping on a solid surface. Some note the substantial weight makes handling challenging.
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How firm is the Rock Hard Super Firm mattress?
It carries Mattress Online's Extra Firm rating, their firmest, described as highly supportive with a very firm, sturdy feel. Owner reviews back this up, with many describing it as feeling like a solid surface. If you're unsure, the 100-night trial lets you test it properly at home.
Does the Rock Hard mattress come with a trial and guarantee?
Yes. Mattress Online offers a 100-night trial, so you can return it if it doesn't suit you, and the mattress is covered by a 10-year guarantee.
What is the Rock Hard Super Firm mattress made of?
It's built from reflex foam with a knitted cover, at a total depth of 23cm. The reflex foam moulds to your body to promote spinal alignment while holding its shape over time. It's handcrafted in the UK and conforms to the BS7177: 2008 fire resistance standard for home use.
What sizes does the Rock Hard mattress come in?
Seven sizes are available: UK Single, Small Double, Double, King, Super King, Emperor and EU King. Prices range from £254 to £588 depending on size.
Is delivery free on the Rock Hard mattress?
Delivery is free to most locations, with next-day delivery on weekdays, a two-hour time slot and a call on delivery day. You can order up to 60 days ahead for a weekday of your choice, or opt for weekend delivery. Room-of-choice delivery costs £20.00 and old mattress recycling £35.00.
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