Available 
Rock Hard Super Firm Foam Mattress, European
from £599.
£599
Sizes tracked: European King
MattressOnline Memory Foam
Rock Hard Super Firm Foam Mattress, Emperor review
Rock Hard Super Firm Foam Mattress, Emperor is a very firm, all-foam option in a large 200cm x 200cm size, with a 23cm depth and retailer trial backing.
Sleep Savvy may earn a commission if you buy through links on this site.
Last verified: 2026-11-04
Quick verdict
Rock Hard Super Firm Foam Mattress, Emperor is a niche buy rather than a broad-appeal mattress: it is built for shoppers who actively want a super-firm feel, full-body support wording and an all-foam construction. At £715 for the Emperor size, it sits at the premium end of the comparison set, so the main question is whether you want this very firm feel badly enough to justify the size premium and the 200cm x 200cm footprint.
Available sizes and prices
Rock Hard Super Firm Foam Mattress, Emperor is listed with 1 size option from £715. Use the table to check the available sizes before clicking through, because retailer availability can change. Always confirm the final checkout price, delivery charge and stock status on the retailer page.
| Size | Firmness | Price | Stock | Last checked | Link |
|---|---|---|---|---|---|
| Rock Hard Super Firm Foam Mattress, Emperor | Firm | £715 | In stock | 2026-11-04 | View |
Key product details
These are the retailer details worth checking first for Rock Hard Super Firm Foam Mattress, Emperor: Brand: MattressOnline; Type: Memory Foam; Firmness: Firm; Price range: £715. Treat them as a quick fact sheet, then use the retailer page to verify any installation, warranty, delivery or model-number details before buying.
| Brand | MattressOnline |
|---|---|
| Type | Memory Foam |
| Firmness | Firm |
| Price range | £715 |
| Owner rating signal | 4.7 out of 5 shown; review volume needs checking with the retailer |
| Last checked | 2026-11-04 |
Product page evidence that matters
MattressOnline describes this model as a full foam block with no springs, single-sided for easier care, and covered in knitted fabric. The Emperor size is listed at 200cm x 200cm with a 23cm depth, and the retailer also highlights a 100-night comfort trial plus a 10-year guarantee. The cover is separately noted as having a 12-month/1-year guarantee, so it is worth checking the exact warranty wording before ordering.
What the wider comparison says
The biggest takeaway is that this Emperor version looks more like a size-and-feel purchase than a value-led one. Benchmark pricing places it above a comparable-product median of £189, with 7 comparable options starting lower and none starting higher, while only 1 tracked variant is listed for this exact product. The visible 4.7/5 rating is encouraging context, but the exact Emperor-only review base is not clearly separated, so it should be treated as supporting evidence rather than a final verdict.
Buyer trade-offs to weigh
The main trade-off is firmness versus cushioning: this MattressOnline model is positioned as super-firm, and at £715 for the Emperor size you are paying for a very specific feel rather than extra plushness. The second trade-off is size versus price, because the 200cm x 200cm Emperor format is larger and more expensive than nearby options such as the £599 European size. Finally, the single-sided design is easier to manage day to day, but the 23cm depth still needs to suit your frame, sheets and any topper you plan to use.
Price and value benchmark
At £715, this sits well above the comparable-product median of £189. In the tracked set, 7 comparable options start lower and none start higher, which tells you this is a premium-priced choice rather than a budget route into firm memory foam. That does not make it poor value automatically, but the value case depends heavily on whether you want the Emperor size, the very firm feel and the retailer trial and guarantee terms.
How it compares with nearby alternatives
The closest comparison is the Rock Hard Super Firm Foam Mattress, European size at £599, which is £116 less than the Emperor. The broader Rock Hard Super Firm Foam Mattress range is listed from £319 to £599, and the Bodyshape Ortho Memory Foam Mattress is a lower-priced alternative in the tracked set. If you are comparing by budget, space and firmness rather than a single headline model name, those nearby options are the clearest reference points.
Review details and confidence
MattressOnline shows a visible 4.7/5 rating with 364 reviews on the product page snippet, but that figure appears to relate to the wider product page rather than a clearly separated Emperor-only review sample. That means the rating is useful background, not strong proof that every size will land the same way for every shopper. It is sensible to treat the review details as supporting context and still verify the exact Emperor details, especially if you are buying the largest size.
Who it suits
This mattress should suit shoppers who want a very firm feel, strong support wording and a straightforward all-foam build. It is especially relevant if you are shopping for a large bed and want the Emperor size at 200cm x 200cm, or if you prefer a simpler single-sided mattress that only needs rotation rather than flipping. It is also a sensible shortlist pick for shoppers who want retailer-backed reassurance such as the 100-night comfort trial and 10-year guarantee.
Who should avoid it
If you want more cushioning, more sink or a softer memory-foam feel, this MattressOnline option is probably not the right match. Side sleepers who prefer a plusher surface may want to compare other firmness levels before buying, and shoppers on tighter budgets will likely find much cheaper memory foam alternatives in the wider market, including the brand’s own Rock Hard range from £319. If you are unsure about very firm mattresses in general, the safer move is to compare it against less rigid options rather than assuming the support wording will suit you.
Comfort and support
MattressOnline positions the Rock Hard Super Firm Foam Mattress, Emperor as a mattress for sleepers who want a super-firm feel and plenty of full-body support. In practical terms, the 23cm-deep, full foam block should feel flatter and less contouring than a softer memory-foam mattress, while the single-sided design makes day-to-day care simpler on a large Emperor size. That support language is useful as a buying clue, but it is still retailer wording rather than a promise of pain relief or a medical outcome, so the key question is whether you want a firmer surface with less sink around the shoulders and hips.
Value verdict
Value here depends less on raw price and more on whether the Emperor size and super-firm feel are exactly what you want. The 100-night comfort trial and 10-year guarantee help the case, but the £715 price point means this is best judged against fit, not just feature count. If you want a very firm, large all-foam mattress and the depth works with your bed frame, the package is more defensible than if you are simply looking for the cheapest memory foam option.
Good alternatives to compare
The closest alternatives to compare with Rock Hard Super Firm Foam Mattress, Emperor include Rock Hard Super Firm Foam Mattress, European, Rock Hard Super Firm Foam Mattress, Bodyshape Ortho Memory Foam Mattress. Use these cards to check whether a nearby model gives you a better price, a more suitable specification or a clearer match for your space and budget.
Available
Rock Hard Super Firm Foam Mattress
from £319-£599.
£319-£599
Sizes tracked: Single, Small Double, Double, King Size, Super King
Available 
Bodyshape Ortho Memory Foam Mattress
from £199-£349.
£199-£349
Sizes tracked: Single, Small Double, Double, King Size, Super King
Retailer details used
Last checked 2026-11-04. The source list below is included to help you check the details behind the comparison. Always confirm the latest price, delivery cost, stock status and product details with the retailer before buying.
More mattresses to compare
These related guides and reviews can help you compare nearby options before buying.
Questions about this mattress
Is the Rock Hard Super Firm Foam Mattress, Emperor too firm for side sleepers?
It may be, especially if you like more cushioning at the shoulder and hip. The retailer positions it as super-firm with full-body support, so side sleepers who prefer a softer sink should compare it carefully against less rigid memory foam options.
Why is the Emperor size more expensive than the European size?
The Emperor is the larger 200cm x 200cm format, and bigger sizes usually cost more because they use more material. In the tracked data, the Emperor is £715 versus £599 for the European size, so the price gap is mainly a size and format difference rather than a different product family.
Is the 4.7/5 rating specific to the Emperor size?
Not clearly. The visible 4.7/5 rating with 364 reviews appears on the wider product page snippet, but the review sample is not shown as Emperor-only. Treat it as useful background, then still check the exact size, price and terms for the Emperor variant before buying.
What does the 23cm depth mean for bed-frame and sheet compatibility?
A 23cm mattress is a useful mid-to-firmer depth, but it still needs to fit your bed frame and fitted sheets properly. MattressOnline also notes that depth can affect suitability for bedding, toppers and frames, so it is worth checking your current setup before ordering.
Does the single-sided design make it easier to care for?
Yes, generally it should be simpler day to day because you only need to rotate it rather than flip it. The retailer specifically describes it as single-sided for easier care, which is handy for a large Emperor mattress that would be awkward to turn regularly.