Mattress Online Rock Hard Mega Firm 1500 Pocket Double Mattress
The Rock Hard Mega Firm 1500 Pocket Mattress does exactly what the name suggests.
- Extra-firm for back & front sleepers
- Handcrafted in the UK, fully recyclable
- 100-night trial & 5-year guarantee
£348
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Mattress Online Rock Hard Mega Firm 1500 Pocket Mattress
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Mattress details
Mattress
Mattress Online Rock Hard Mega Firm 1500 Pocket Mattress
Size
Firmness
Firm
Construction
Pocket Spring
Orthopaedic
Depth (cm)
25
Layers
2
Layer Details
Comfort Layer
Soft white fibre fillings, finely filled with high density compressed polyester. This gives a thin layer of cushioning over the springs, which means you'll feel comfort at the surface but firmness underneath rather than a plush, sink-in feel.
Support System
1500 pocket springs that gently contour around your body for personalised support. Because each spring moves independently, you get support matched to your shape and less motion transfer if you share the bed.
Layer details from mattressonline.co.uk product page, September 2026.
Key benefits
- Shared sleep without shared movement: The pocket springs move independently, which means a partner turning over on their 67.5cm each side is far less likely to wake you.
- Fits the typical UK bedroom: At 135 x 190cm, we suggest a room of at least 2.6m x 2.8m, which most British bedrooms can manage with space to walk round.
- Room for bedside tables: Because a UK double leaves more floor either side than a UK king, most rooms still take a table and lamp on both sides.
- Firm edges you can use: Steel piping around the perimeter helps the sides hold their shape, useful in a double where two sharers each end up near an edge.
- Easy to dress and move: Double bedding is stocked everywhere at every price, and the 4ft 6in x 6ft 3in footprint is easier to get up a tight staircase than larger sizes.
This size suits you if...
You share the bed every night and both prefer a properly solid, extra-firm feel, or you sleep alone and want space to stretch without giving the bed the whole room. It also suits a guest room that hosts visiting couples, provided your guests won't mind a surface with very little give. Your bedroom should be at least 2.6m x 2.8m by our guidance.
Consider another size if...
You and your partner are both average build or larger and 67.5cm each feels tight night after night. We'd recommend the UK king instead: it gives 75cm each, and we suggest a room of at least 2.7m x 2.9m for it.
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FAQ's
Is the UK double Rock Hard Mega Firm big enough for a couple?
For most couples, yes. The UK double gives 67.5cm each for two people sharing, which has been the British standard for decades. The 1500 pocket springs also limit motion transfer, so movement on one side stays on that side. If either of you is broad-shouldered or a restless sleeper, the UK king gives 75cm each.
What room size do I need for the Rock Hard Mega Firm in a UK double?
We suggest at least 2.6m x 2.8m, with around 3m x 3m the comfortable norm. That allows walking space on both sides and, in most rooms, bedside tables too. If your room is smaller, the UK small double is 15cm narrower and the same length, and we suggest at least 2.4m x 2.8m for it.
Should I get this mattress in a UK double or a UK king?
The UK double is 15cm narrower and 10cm shorter than the UK king, and the UK king gives 7.5cm more width each for two sharing. Choose the UK double if your room is modest or you want space around the bed; choose the UK king if you share nightly and either of you is tall or sleeps spread out.
Is a double a good size for a firm guest room mattress?
It works well. A UK double accommodates visiting couples as well as solo guests, and the extra-firm feel suits back and front sleepers for short stays. Bear in mind that lightweight side sleepers may find it hard at the shoulder and hip, so it's a better guest bed if your visitors tend to prefer firmer support.
Will the double size fit up a narrow staircase?
At 135 x 190cm, or 4ft 6in x 6ft 3in, the UK double is the largest common size that usually manages turning stairs in older terraces and tight new build landings without drama. Measure your narrowest turn before ordering, and check the retailers listed on this page for their delivery access guidance.