Mattresses I slept on the firmest mattress you can buy in 4th of July sales — here’s why it’s a dream for easing back pain Deals By Ruth Jones Published 4 July 2026 The Plank Firm mattress is back to its lowest price of the year in the 4th of July sale, with up to $460 off When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works . (Image credit: Future) Copy link Facebook X Reddit Email Share this article 0 Join the conversation Follow us Add us as a preferred source on Google Newsletter Subscribe to our newsletter When I slept on the Plank Firm mattress, now from $524 in the Plank 30% off 4th of July sale , I was most impressed by the full-body support. From my shoulders and lower back to my and hips and toes, my body was lifted and straightened, helping undo some of the tension from hunching over my desk all day. The Plank is a slightly unusual mattress. Actually, it’s very unusual. Not only is it a firm all-foam bed, it’s also double-sided, meaning you can flip between Firm and Extra Firm feels. While the best mattresses we’ve tested tend to be crowd pleasers, the Plank is targeted at a specific audience: those who want a harder mattress that feels like its straightening out their spine. If you’re looking for a firm bed in today’s 4th of July mattress sales , I don’t think you’ll find a better option than the Plank (especially as its back to its cheapest price of the year). Here’s why… Save 30% Plank Firm (twin): was $749 now $524.30 at Plank Mattress Plank’s 30% off sale matches the best deal we’ve seen this year and brings the Plank back to its lowest price of 2026. A queen is now $932.40 (was $1,332) and comes with a 120-night trial and lifetime warranty. It’s a good price for a specialist mattress — as a dual-sided bed with an Extra Firm feel described as ‘the firmest mattress on the market,’ it holds an almost unique place in the sleep world. Our Plank Firm mattress review : ★★★★½ User score : ★★★★½ (4,100+ reviews) View Deal Today’s best Plank Firm Mattress deals $749 View Deal Plank Firm Mattress – Twin $999 View Deal Plank Firm Mattress – Full $1,332 View Deal Plank Firm Mattress – Queen $1,532 View Deal Plank Firm Mattress – King We check over 250 million products every day for the best prices Excellent support to ease back pain I’d describe the Plank Firm’s support as ‘unyielding.’ That might not sound like a compliment at first but it describes how the Plank Firm is able to hold my body in a completely straight line from head-to-toe. It’s this feature that earned it the title of the best firm mattress of 2026. Unyielding support means there’s no sagging, sinking, or dipping that might put unwelcome strain on parts of the spine. Because my body doesn’t have to work to hold itself up, it can get on with what sleep is meant for: rest and repair. Ideal for back and stomach sleepers While side sleepers tend to benefit from a softer bed (you’ll find our top picks in our best mattress for side sleepers guide), back and stomach sleepers often need something firmer. (Image credit: Future) When you lie on your back or front on a softer bed, your hips tend to sink lower than the rest of your body. This puts pressure on the spine and can cause long-term discomfort. But a firm bed, like the Plank mattress, keeps those hips lifted. It’s particularly good for stomach sleepers (our best stomach sleeper mattress guide is dominated by firm beds). Stomach sleeping already puts your spine in odd positions — you don’t want your mattress to make it worse. Strong from edge-to-edge Edge support refers to how sturdy a mattress is at the perimeter. Strong edges allow you to stretch out and make it easier to climb in and out of bed. Firm mattresses don’t always have good edge support but the two do tend to go hand in hand (when there’s less sink in general, the edges are less likely to collapse). The Plank Firm has exceptional edge support. I always sit on the side of the bed while getting my
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