Sierra Sleep by Ashley
Sierra Sleep Millennium Luxury Plush Gel Latex Hybrid Mattress
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The Millennium Luxury Plush Gel Latex Hybrid is Sierra Sleep's answer for sleepers who want a plush, cushioned top layer without giving up the support of a real coil system underneath. If your last plush mattress left you feeling like you were sinking into it rather than resting on it, this Ashley build, model M508, is worth a close look.
How it's built
The comfort side starts with a soft 4-way stretch knit cover, then two layers of phase change material positioned right at the surface to pull heat away as soon as you lie down. Below that sits two inches of copper-infused memory foam for pressure relief with a little extra help managing warmth, then three inches of sculpted, body-contouring foam that cushions the shoulders and hips. A gel latex layer follows, adding a responsive bounce that helps the mattress recover its shape as you move and shift through the night. All of that comfort sits on a wrapped coil support system built around a pressure-sensitive NanoCoil unit and individually wrapped coils, so each coil flexes on its own instead of pulling on its neighbors. The whole mattress stands 15 inches tall and works on an adjustable base if that is part of your setup.
Feel and support
This is a plush bed by design, the comfort layers are deep enough that you settle in rather than sit on top, but the coils underneath keep that settling from turning into a sag. Side sleepers get real cushioning at the shoulder and hip where they need it most, and the individually wrapped coils help keep the spine level even as the top layers do their job. Because it's a hybrid and not an all-foam mattress, it also moves a little more air and sleeps cooler than a dense foam bed would at the same softness, and the phase change layers add another layer of temperature management on top of that.
Who it suits
- Side sleepers who want cushioning at the shoulder without losing support at the hip
- Back sleepers who like a softer surface but still want a coil system underneath them
- Combination sleepers who move between their side and back and want a bed that doesn't fight either position
- Sleepers switching from an old, worn-out plush bed and looking for that same soft feel with fresher support
It's probably not the right match if you sleep mostly on your stomach or you generally prefer a firmer, more minimal-sink surface. Ashley builds firmer options into the Sierra Sleep line for that kind of sleeper.
Series: Millennium Luxury Plush Gel Latex Hybrid (Ashley model M508). The best way to know if a plush hybrid is right for your body is to lie on it. Stop by any Mattress Overstock showroom across Kentucky and spend a few minutes on this exact mattress before you decide.
What makes this mattress different
Dual phase change cooling
Two layers of phase change material sit right at the surface, pulling heat away the moment you lie down instead of waiting for foam to catch up.
Copper-infused pressure relief
Two inches of copper-infused memory foam cushions the shoulders and hips while helping draw warmth off the surface.
Sculpted comfort foam
Three inches of sculpted, body-contouring foam shapes itself around your frame for a plush, cushioned feel.
Gel latex responsiveness
A gel latex comfort layer adds bounce and helps the mattress recover its shape quickly as you change positions.
NanoCoil wrapped support
A pressure-sensitive NanoCoil unit works with individually wrapped coils, so each coil flexes on its own and limits motion transfer across the bed.
4-way stretch knit cover
A soft, breathable cover stretches in every direction for a smooth sleep surface that moves with you.
Adjustable base compatible
The 15 inch profile works on an adjustable base as well as a standard platform or foundation.
Made in the USA
Backed by a 10-year non-prorated warranty and built domestically.
Plush comfort layered over real coil support
From the top down, the Millennium Luxury Plush starts with a 4-way stretch knit cover, then two layers of phase change material built to pull heat away right where your body meets the bed. Next comes two inches of copper-infused memory foam for pressure relief, followed by three inches of sculpted comfort foam that contours around the shoulders and hips. A gel latex layer sits underneath that, adding responsiveness and helping the mattress spring back into shape as you move. All of that rests on a wrapped coil support system built around a pressure-sensitive NanoCoil unit and individually wrapped coils, so the base can contour and support independently of the softer layers above it. The full mattress measures 15 inches tall.
If plush isn't quite your feel, ask the floor team about firmer options in the Sierra Sleep by Ashley lineup.
See the full Sierra Sleep by Ashley lineup →Built for the side and back sleeper who wants to sink in
Side sleepers: the copper-infused and sculpted comfort foams cushion the shoulder and hip, the two spots that need the most give in this position.
Back sleepers: the plush top layers still sit over a full coil system, so your hips stay supported instead of sinking past where they should.
Combination sleepers: the gel latex layer adds enough responsiveness that shifting from your side to your back doesn't feel like fighting the mattress.
Sleepers replacing an old, worn plush bed: this gives you that familiar soft feel with fresher foam and a coil system underneath doing more of the work.
Hot sleepers who still want plush: two layers of phase change material plus copper-infused foam are built to manage heat, so a soft feel doesn't have to mean a warm one.
Probably not for you if: you sleep mainly on your stomach or you prefer a firm, minimal-sink surface. Ask about a firmer option in the Sierra Sleep by Ashley lineup instead.
Specifications
| Height | 15 in |
|---|---|
| Feel | Plush |
| Firmness | Plush, softer than Sierra Sleep's medium and firm hybrid models |
| Construction | 4-way stretch knit cover over phase change material, copper-infused memory foam, sculpted comfort foam, and a gel latex layer, above a wrapped coil system built around a NanoCoil unit and individually wrapped coils. 15 inches total height. |
| Cooling | Two layers of phase change material at the surface plus copper-infused memory foam work together to pull heat away from a plush top layer. |
| Motion isolation | Individually wrapped coils flex independently to limit motion transfer, though as a hybrid it carries a bit more movement than an all-foam mattress. |
| Warranty | 10-year non-prorated warranty |
Frequently asked questions
How firm is the Millennium Luxury Plush Gel Latex Hybrid?
It's built plush, on the softer end of Ashley's hybrid lineup. The comfort layers, phase change material, copper-infused memory foam, sculpted foam, and gel latex, are deep enough that you settle into the surface, while the coil system underneath keeps that settling from turning into a sag.
Is this a memory foam mattress or a hybrid?
It's a hybrid. The top is built from foam and gel latex comfort layers, but support comes from a wrapped coil system with a pressure-sensitive NanoCoil unit and individually wrapped coils, not from foam alone.
Does it sleep hot?
It's built to manage heat: two layers of phase change material sit right at the surface, and the comfort foam underneath is copper-infused, both aimed at pulling warmth away from a plush surface that would otherwise trap it.
How much motion transfer is there?
Individually wrapped coils flex on their own, which limits how much movement crosses the bed compared to a standard innerspring. As with any hybrid, it carries slightly more motion than an all-foam mattress, but the wrapped coil design is built to keep that in check.
Can I use this mattress on an adjustable base?
Yes. The 15 inch profile is built to work with adjustable bases as well as a standard platform or foundation.
What sizes is this available in?
Twin XL, Queen, King, and California King.
Does this mattress come with an at-home trial?
No. Sierra Sleep beds sold at Mattress Overstock do not include an at-home trial period. The showroom is where you try before you buy: come lie on this exact mattress in your own sleeping position so you know how the plush feel and coil support feel under your body before it goes home with you.
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. Stop by and spend a few minutes on this exact mattress before you decide.
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.
