Mattress Online Rock Hard Mega Firm 1500 Pocket Mattress
Mattress
Mattress Online Rock Hard Mega Firm 1500 Pocket Mattress
Size
Firmness
Firm
Construction
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.
- Real width for one sleeper: At 120cm across, the UK small double is 30cm wider than the UK single, which means genuine room to stretch without moving to a bigger frame.
- Fits rooms a double crowds: It's 15cm narrower than a UK double, so it suits box rooms, studio flats and loft conversions where every centimetre of floor space matters.
- Firm support across the full surface: The 1500 pocket springs respond to your body individually, so a solo sleeper gets firmer pushback where they're heavier wherever they settle on the wider surface.
- Steel piping keeps the edges usable: Edge support around the perimeter means the sides hold their shape, useful when a compact room forces you to sit or sleep near the edge.
- Standard 4ft sizing: The small double is a standard UK size, so frames, fitted sheets and bases are easy to find.
This size suits you if...
You're a solo sleeper who wants a firm, solid surface and more width than a UK single, or you're furnishing a compact second bedroom, guest room or loft conversion where a full double would leave no walking space. It also suits a teenager who has outgrown a single but whose room can't spare the extra 15cm a UK double takes.
Consider another size if...
You share the bed every night. The UK small double works for the occasional stay, but for nightly sharing we'd recommend the UK double instead, which gives 67.5cm each and needs a room of at least 2.6m x 2.8m.
Similar Mattresses in This Price Range
Did you know? On Mattress Unboxed we have over 1,000 different mattresses to suit all types of sleepers. View all mattresses.
Is a UK small double big enough for the Rock Hard Mega Firm 1500?
For one adult, comfortably. At 120 x 190cm you get 30cm more width than a UK single, and the extra-firm feel is consistent across the surface because the 1500 pocket springs move independently. Two people can share for an occasional night, but for regular sharing the UK double is the better fit.
What room size do I need for the Rock Hard Mega Firm in a small double?
We suggest allowing at least 2.4m x 2.8m. That leaves enough space to walk round the bed and open drawers or a door. If your room is tighter than that, check the door swing carefully first: in a box room or studio, the mattress width often decides whether the door still clears.
Is the small double Rock Hard Mega Firm good for a guest room?
Yes, provided your guests are happy with an extra-firm feel. The size suits guest rooms well: couples can share for a weekend without the room being dominated by a full double frame. The firmness is the thing to weigh up, since side sleepers and anyone who prefers a soft, cushioned surface may find it unforgiving.
How much smaller is the UK small double than a UK double?
The UK small double is 15cm narrower than the UK double, and both are the same 190cm length. That 15cm sounds modest, but in a compact bedroom it can be the difference between a clear path to the window and shuffling sideways. For nightly sharing, the UK double gives 67.5cm each.
Can a teenager use the Rock Hard Mega Firm 1500 small double?
It can work well for a teenager who has outgrown a single, since the UK small double adds 30cm of width without taking up any extra length. The caveat is the feel: this is an extra-firm mattress by design, so a lighter teen who sleeps on their side may find it too hard at the shoulder and hip.