EmmaDiamond Hybrid Deluxe

How we test performance

We rate overall mattress performance by combining the results of six individual tests. We measure how well the mattress keeps your body in a natural position when you're lying on your side or back and combine these into an overall body support score. We also rate how easy it is to roll over on the mattress and how breathable it is – more breathable mattresses will not get damp with sweat. Finally, we measure stability to assess how much you'll notice the mattress moving when your partner turns on it - good mattresses are more stable.

How we test durability

To test how durable mattresses are, we simulate years of use by rolling a heavy barrel over them thousands of times. We then assess each mattress for damage and change in height, firmness and body support to see how well they stand the test of time. Good mattresses will stay the same as when you first bought them. The overall durability score is a combination of the individual ratings. Change in height shows how much the mattress sagged in our durability test and change in firmness measures if the mattress got harder or softer. Change in body support indicates whether the mattress offers the same level of support after years of use. Finally, we rate whether or not the mattress was damaged after our durability tests.

How we test ease of use

Most mattresses need turning over or rotating from time to time, so we rate how easy it is to move and turn the mattress by considering factors like weight and whether there are any handles.

How we test build quality

How well constructed the mattress is.

How we test brand comfort

This is not a comfort score for this individual mattress, and does not contribute to the overall test score. We cannot test mattresses for comfort because everyone has a different opinion on what is comfortable. In October 2023, we asked 3,530 Which? members in an online survey, who own a mattress from this brand, to rate it for comfort. The star rating shows whether the general consensus was positive or not, and can be used as a guide to this brand as a whole. Go to our mattress brand guides for more information, and bear in mind that you should make every effort to try a mattress before you buy.