Sierra Sleep by Ashley
Sierra Sleep Comfort Plus Mattress (M51811)
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The Sierra Sleep Comfort Plus is a straightforward call: if you want a true medium coil hybrid that keeps its shape without stretching your budget, this is one of the more sensible beds in the Sierra Sleep line.
The Build
Ashley builds the Comfort Plus around a wrapped coil base topped with a single layer of gel infused memory foam. The gel foam softens the surface and pulls heat away better than a plain foam layer would, while 680 individually wrapped coils sit underneath, each one able to move on its own instead of dragging its neighbors down with it. That independence is what keeps motion on one side of the bed from traveling to the other. Reinforced coils run the perimeter, so the edge holds up when you sit down to tie your shoes or a partner rolls toward the side of the bed. Ashley finishes the mattress in a soft, stain treated stretch knit cover in gray, and it is a tight top design, meaning the comfort layer is quilted flush into the cover rather than stacked as a separate pillow top. That keeps the surface even and simple to dress with a fitted sheet. This is the entry point of the M518 Comfort Plus series, built to be a dependable coil hybrid rather than a specialty bed.
Feel and Support
Expect a medium feel: enough gel foam on top to cushion the shoulders and hips, enough coil underneath to keep the spine level instead of letting the hips sink. Back sleepers tend to do well here, since the coils hold the midsection up while the foam takes the edge off. Side sleepers get a reasonable amount of give at the shoulder, though anyone who wants a deep contouring hug should look at a bed with a thicker foam layer. Like any coil hybrid, the Comfort Plus sleeps a little cooler than an all foam mattress, since air moves through the coil layer instead of getting trapped against a solid foam core.
Who It Suits
- Back sleepers who want real support without a hard, flat feel
- Side sleepers who like a little coil bounce along with their cushioning
- Shared beds where motion transfer and edge support both matter
- Anyone who wants a mattress they can pair with an adjustable base to raise the head or feet
Skip it if you specifically want a deep memory foam hug with no coil feel at all, or if you sleep only on your stomach and want a firmer surface than medium.
Getting It Home
Like most mattresses in this category, the Comfort Plus compresses and ships in a box for easier delivery and setup. Give it a full day to expand once it is unboxed before you judge the final feel, since a compressed mattress needs time to fully loft.
Firmness is personal, and a description only takes you so far. Come lie on the Comfort Plus at one of our Kentucky showrooms in your own sleeping position, in your own clothes, for as long as you want, before you decide.
What makes this mattress different
Gel infused memory foam comfort layer
A gel infused memory foam layer sits on top for pressure relief at the shoulders and hips, with better heat dispersion than a plain foam layer of the same thickness.
680 individually wrapped coils
Each coil is wrapped and moves on its own instead of dragging its neighbors down with it, which is what keeps a partner's movement from traveling across the bed.
Reinforced perimeter coils
Stronger coils run the edge of the mattress, so the usable sleep surface holds up closer to the border instead of collapsing when you sit down to get dressed.
Tight top construction
The comfort layer is quilted flush into the cover rather than stacked as a separate pillow top, so the surface stays smooth, even, and easy to dress with a fitted sheet.
Soft stretch knit cover
A stain treated stretch knit cover in gray wraps the mattress, giving it a clean, low-maintenance surface that resists everyday spills.
Medium feel for most sleep positions
The coil and foam combination lands at medium, supportive enough for back sleepers and cushioned enough for most side sleepers.
Adjustable base compatible
The wrapped coil construction works with an adjustable base if you want to raise your head or feet, without changing the feel of the mattress.
Ships compressed in a box
Arrives compressed and rolled for a simpler delivery; unwrap it and give it a full day to expand before judging the final feel.
A medium coil hybrid built on the basics done right
The Comfort Plus is Ashley's M518 series, the entry point of the Sierra Sleep coil hybrid lineup, and the construction keeps things simple on purpose. From the top down, a soft stretch knit cover wraps a single layer of gel infused memory foam, quilted flush into the cover in a tight top design rather than built up as a separate pillow top. That gel foam layer softens the surface at the shoulders and hips and pulls heat away better than a plain foam layer would.
Underneath sits the mattress's real workhorse: 680 individually wrapped coils. Because each coil is wrapped and free to compress on its own, the coil layer responds to your body's shape point by point instead of flexing as one connected unit, and it keeps a partner's movement from traveling across the bed. Reinforced coils run the perimeter, so the edge of the mattress holds up when you sit down rather than folding in on itself. It is a straightforward hybrid: one comfort layer for cushioning, a full coil system underneath for support and airflow, nothing extra layered in between.
See the full Sierra Sleep lineup →A medium feel built for back sleepers, with room for side sleepers too
Back sleepers: this is the position the Comfort Plus suits best. The wrapped coils keep the midsection lifted and the spine level, while the gel foam layer softens the surface just enough that it doesn't feel flat.
Side sleepers: the gel memory foam gives the shoulders and hips somewhere to settle, and most side sleepers find a medium coil hybrid like this one comfortable, though anyone who wants a deep foam hug should look at a thicker comfort layer.
Shared beds: 680 individually wrapped coils plus reinforced perimeter coils mean less motion transfer and more usable edge, both things that matter when two people share one mattress.
Adjustable base users: the coil and foam construction works with a base that raises the head or feet, so it is a fair pick if that is part of your setup.
Hot sleepers: the gel infusion in the comfort layer and the open coil layer underneath both help move heat away from the surface better than a dense all foam mattress would.
Probably not for you if: you sleep only on your stomach and want a firmer, flatter surface than medium, or you specifically want a deep memory foam contour with no coil response at all.
Specifications
| Feel | Medium |
|---|---|
| Firmness | Medium, a balanced feel for back and side sleepers |
| Construction | Gel infused memory foam comfort layer quilted into a tight top cover, over a base of 680 individually wrapped coils with reinforced perimeter coils. |
| Cooling | The gel infused memory foam comfort layer pulls heat away from the surface, and the open wrapped coil layer underneath allows more airflow than a solid foam core. |
| Motion isolation | Good: 680 individually wrapped coils move independently, so a partner shifting or getting up is less likely to travel across the bed. |
| Warranty | 10-year non-prorated warranty |
Frequently asked questions
How firm is the Sierra Sleep Comfort Plus?
It sits at medium: firm enough that back sleepers stay supported, soft enough that the gel memory foam layer cushions the shoulders and hips for side sleepers. It is not a plush, deep-sink bed, and it is not a hard, flat one either.
Who is this mattress best for?
Back sleepers get the most out of the coil support underneath, and most side sleepers find the gel memory foam layer cushions well enough to be comfortable. Stomach sleepers who prefer a firmer, flatter surface may want to look at a firmer model instead.
Is this a memory foam mattress or a hybrid?
It is a hybrid. A single layer of gel infused memory foam sits on top of 680 individually wrapped coils, so you get pressure relief from the foam and the support and airflow of a full coil system underneath, not an all foam build.
Does it sleep hot?
It should sleep cooler than a plain all foam mattress. The comfort layer is gel infused, which pulls heat away from the surface better than standard foam, and the open wrapped coil layer underneath allows more airflow than a solid foam core.
Is it good for a shared bed?
Yes. The 680 individually wrapped coils move independently, which cuts down on motion transfer when a partner shifts or gets up, and the reinforced perimeter coils keep the edge from collapsing when either of you sits on the side of the bed.
Can I use this with an adjustable base?
Yes, the wrapped coil construction is compatible with an adjustable base if you want to raise your head or feet. If you are not sure which base fits your frame, our showroom team can walk through the options with you.
How is it shipped and set up?
It ships compressed and rolled in a box for easier delivery and setup. Unwrap it, let it unroll, and give it a full day to expand before you judge the final feel.
Does this mattress come with an at-home trial?
No. Sierra Sleep beds, including the Comfort Plus, do not include an at-home trial. The honest way to know if the feel works for you is to lie on this exact mattress at one of our Kentucky showrooms, in the position you actually sleep in, before you buy.
Can I see this mattress in person near me?
Yes. Mattress Overstock is a Kentucky owned company with showrooms in Lexington, Georgetown, Somerset, London, and Richmond. Come lie on the Comfort Plus in your own sleeping position before you decide, and delivery is available across our Kentucky service area.
Buy it from people you can actually visit
- Free local delivery To your home across Central & Eastern Kentucky.
- Free setup We place and set up your new bed in the room.
- Free old-mattress haul-away The old one goes out the same day the new one comes in.
Independently owned in Kentucky since 2012. Walk in any day (no appointment) and someone who actually knows the floor will help you find the right fit.
Still deciding?
Try it in person at any Kentucky showroom
Walk into any Mattress Overstock location, lie down, and feel the difference yourself. No appointment, no pressure. Our team has over 100 years of combined mattress experience and we're here to help you find the right fit.
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