UnboxingThe topper arrives wrapped up (Alice Reynolds/The Independent)The Simba cooling topper arrives compressed, rolled, and tightly wrapped in plastic inside a cardboard box. Ripping the plastic away from it, the topper stays folded until you peel the layers away. This made it easy to move on top of my bed and roll out onto my mattress to expand.It was pretty quick to take shape and I was able to sleep on it in the evening of its delivery. The off-gassing smell is one thing to take note of as it’s quite strong and lingers for a while – though opening the windows helped air the room. The mattress topper was a dream to fix to my mattress, with four elasticated straps for each corner that secure it in place.DesignAt 6.5cm, the topper adds a noticeable thickness to the bed (Alice Reynolds/The Independent)Simba’s cool foam topper has three key layers. The top is a knitted cover that is irresistibly soft and underneath is the brand’s patented Simbatex foam layer. The latter is the brand’s take on a memory foam, which gives the same contouring feel but adds cooling and breathability. Below this a contoured base, which has a peaked structure that restores air flow. Comparing it to the hybrid mattress topper from Simba (which is our best mattress topper), the design is simpler and focuses more on comfort and breathability than support, as it misses the hybrid’s microspring layer. At a thick 6.5cm depth, it’s a considerable addition to your bed – one that feels like a slim mattress rather than just a layer.ComfortThe topper has a softer feel (Alice Reynolds/The Independent)The Simba cool foam topper provided maximum comfort and completely transformed my old, overused mattress I was handed down with my rented room. I was battling popping springs and a dip down the middle, but the topper made my mattress anew for a fraction of the price of a new mattress. Two months in, the dip has slightly returned and a new mattress is definitely due, but the supreme comfort offered by the topper is still great.The first layer is supple, while the rest provides enough support for me as someone without any aches and pains. While Simba say it offers a medium-firm feel, I would say it’s on the softer side. If you need a more solid base to support you, our tester found the Simba hybrid mattress topper to offer “brilliant pressure relief, spinal support and just enough sink to cushion your pressure points”. The level of comfort I experienced when sleeping on the cool foam topper improved my sleep and levelled up the comfort of my bed.BreathabilitySimba’s new cool foam topper aims to fill the cooling gap in its range and as someone who generally sleeps warm, my attention was piqued. Putting it through its paces, I tested the cooling topper through both of this summer’s heatwaves but I wasn’t overly impressed by the cooling performance. Its breathability comes down to two design features: its foam middle layer that’s graphite-infused and the base that has a contoured texture, which creates pockets of space to allow air to flow freely.It wasn’t enough to keep me cool throughout the night, especially when it was red hot that day, but I found it helped to lower my body’s temperature making it easier to fall asleep. When sharing the bed, I found its cooling potential further reduced.CareTaking care of the topper is easy, as the top zip-off cover is machine washable at 40C on a reduced spin cycle. Note, you can’t tumble dry or iron it. The base fabric can also be cleaned using a damp cloth in small circular motions. To protect and extend the life of your mattress topper, I’d recommend layering one of the best mattress protectors on top. Key specificationsSizes: Single, small double, double, king, super kingDepth: 6.5cmCare: Cover is removable and machine washable up to 40C