Mattress Online Rock Hard Super Firm Foam Mattress

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 a mid-range starting price. Delivery is free to most locations, with next-day weekday delivery, a two-hour time slot and the option of paid room-of-choice delivery. Old mattress recycling is available for an extra charge, which takes one chore off your list.

Back sleepers
The very firm reflex foam gives a solid, stable surface that keeps you feeling supported rather than sinking in, which suits lying flat on your back.

Front sleepers
A 23cm build with an Extra Firm rating means the surface barely gives, so your middle stays level instead of dipping into the mattress.

Heavier sleepers
Durable, resilient reflex foam holds its shape for an extended period, which means a sturdy feel that should keep working under more weight.

Budget buyers
The copy calls it one of the more affordable ways to get genuine extra-firm support, with a 10-year guarantee and a 100-night trial.

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.

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.

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 and old mattress recycling cost extra.