Sierra Sleep by Ashley
Sierra Sleep Millennium 2.0 Hybrid 16 Inch Mattress
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The Sierra Sleep Millennium 2.0 Hybrid 16 Inch is for sleepers who want to sink into a mattress, not just lie on top of it: an ultra plush hybrid that pairs deep foam cushioning with a real coil core underneath.
How It's Built
- Hyper Cool 4-way stretch knit cover woven with phase changing material (PCM) that pulls heat off the surface as you settle in
- High-density gel memory foam layer under the cover, built for lumbar support and pressure relief through the lower back
- Second layer of high-density body-contouring foam that cushions the shoulders and hips, the two spots that make or break a plush mattress
- Premium pressure-sensitive NanoCoil unit of individually wrapped coils beneath the foam, adding targeted support and cutting down motion transfer between sleepers
- Stability support base at the bottom that reinforces the edge and helps the mattress hold its shape over time
- 16 inches of total height, built and assembled in the USA
The order of the layers is what makes the plush feel work long term. Gel memory foam gives the top of the bed its slow, cloud-like give, the body-contouring layer beneath it fills in around the shoulders and hips instead of bottoming out flat, and the individually wrapped coils underneath both layers are doing the real work of keeping your spine level while all of that softness happens above them. The PCM-infused cover matters more on an ultra plush bed than a firm one, since more of your body stays in contact with the surface through the night, and it is built to keep that contact from turning into trapped heat.
Who It's For
Back and side sleepers who like generous cushioning around the shoulders and hips will feel the difference right away, especially if the mattress you are replacing was too firm and left you shifting to find a comfortable spot. It also suits two people sharing a bed where one partner moves around at night; the wrapped coil unit is built to isolate that motion instead of carrying it across the mattress.
Stomach sleepers, and anyone who needs firmer support to keep their hips from sinking, should look at a firmer model in the Sierra Sleep lineup instead. An ultra plush bed is not built for that kind of alignment, and we would rather steer you to the right mattress than sell you this one anyway.
It ships compressed in a box and needs up to 48 hours to fully expand once it is unboxed. It works with adjustable bases, and it needs nothing beyond unboxing to go onto a frame or foundation.
Ultra plush is a feel you have to test with your own body; a description only gets you so far. Come lie on the Millennium 2.0 Hybrid at one of our Kentucky showrooms in your usual sleeping position, that is the only real way to know if it is the one.
What makes this mattress different
Ultra plush over a real coil core
This is a hybrid, not a foam mattress: an ultra plush comfort stack sits on top of a genuine wrapped coil support system, so the softness on top does not come at the cost of support underneath.
PCM cooled stretch knit cover
The Hyper Cool 4 way stretch knit cover is woven with phase changing material (PCM), pulling heat away from the surface as your body settles in for the night.
High density gel memory foam
A gel memory foam layer sits just under the cover, built for lumbar support and pressure relief through the lower back.
Body contouring comfort foam
A second high density foam layer cushions the shoulders and hips specifically, the two pressure points that make or break a plush mattress over time.
NanoCoil wrapped coil support
A premium pressure sensitive NanoCoil unit of individually wrapped coils sits beneath the foam, adding targeted support and cutting down motion transfer if you share the bed.
Reinforced edge and base
A stability support base runs the perimeter, reinforcing the edge so the mattress holds its shape instead of breaking down early.
Ships compressed, ready in 48 hours
The mattress compresses into a box for delivery. Once unboxed, give it up to 48 hours to fully expand before you sleep on it.
Adjustable base compatible
The hybrid build works on adjustable bases as well as a standard frame or foundation, with no assembly needed beyond unboxing.
An ultra plush surface built over a real coil core
The Millennium 2.0 Hybrid layers its comfort from the top down: a Hyper Cool 4 way stretch knit cover infused with phase changing material, then a high density gel memory foam layer for lumbar support, then a second high density foam layer built to contour around the shoulders and hips. Underneath all of that sits the part that keeps it from being just a soft foam bed: a premium pressure sensitive NanoCoil unit of individually wrapped coils, backed by a stability support base that reinforces the edge.
That order is deliberate. The foam layers give the bed its ultra plush feel and absorb pressure at the shoulders and hips, while the wrapped coils underneath keep your spine level and add a layer of motion isolation the foam alone cannot provide. It is 16 inches of total height, ships compressed in a box, and needs up to 48 hours to fully expand once it is unboxed.
See the full Sierra Sleep lineup →Built for sleepers who want to sink in
Back sleepers: the gel memory foam and body contouring layer cushion the lower back and hips while the coils underneath keep your spine from sagging, a combination that suits back sleepers who still want softness on top.
Side sleepers: the deep foam comfort layers give the shoulders and hips somewhere to sink in, which is exactly what side sleepers need to keep pressure off those joints.
Anyone upgrading from a firm bed: if your last mattress was too hard and you spent the night shifting to find a comfortable spot, this is the kind of softness you have been missing.
Couples sharing a bed: the individually wrapped NanoCoil unit is built to isolate movement, so one partner getting up or turning over is less likely to disturb the other.
Hot sleepers who also want plush: the PCM infused cover pulls heat off the surface, which matters more here than on a firm bed since more of your body stays in contact with an ultra plush surface all night.
Probably not for you if: you sleep on your stomach or need firm support to keep your hips from sinking. An ultra plush bed is not built for that kind of alignment, and a firmer model elsewhere in the Sierra Sleep lineup will serve you better.
Specifications
| Height | 16 in |
|---|---|
| Feel | Ultra Plush |
| Firmness | 2 out of 10 (10 = firmest) |
| Construction | Hyper Cool 4-way stretch knit cover with PCM, over high-density gel memory foam and high-density body-contouring foam, over a NanoCoil unit of individually wrapped coils, on a stability support base: 16 inches total. |
| Cooling | Phase changing material (PCM) woven into the Hyper Cool stretch knit cover pulls heat off the surface, and the gel memory foam layer underneath keeps the plush feel from trapping warmth. |
| Motion isolation | Good for a plush hybrid: the individually wrapped NanoCoil unit flexes coil by coil to isolate movement, though not as completely as an all-foam bed. |
| Warranty | 10-year non-prorated limited warranty |
Frequently asked questions
How firm is the Sierra Sleep Millennium 2.0 Hybrid?
It is built to an ultra plush comfort level, the softest end of the scale. Two layers of high density foam sit over the coil unit, so you sink in at the shoulders and hips while the wrapped coils keep your spine supported underneath.
Is this a memory foam mattress or a hybrid?
It is a hybrid. The comfort layers are high density gel memory foam and body contouring foam, but underneath them is a premium pressure sensitive NanoCoil unit of individually wrapped coils, not a solid foam core.
Does it sleep hot?
The Hyper Cool 4 way stretch knit cover is woven with phase changing material (PCM) that pulls heat away from the surface, and the gel memory foam layer is built to keep the plush feel from trapping warmth the way older foam beds could.
Is it good for couples?
The individually wrapped coils in the NanoCoil unit are designed to isolate motion, so movement on one side of the bed is less likely to carry across to the other side.
Will it work with my adjustable base?
Yes. The mattress is built to work with adjustable bases as well as a standard frame or foundation.
How is it delivered, and does it need time to set up?
It ships compressed in a box. Once you unbox it, give it up to 48 hours to fully expand before sleeping on it. No assembly is required beyond that.
Do you offer an at-home trial on this mattress?
No. Sierra Sleep mattresses at Mattress Overstock do not include an at-home trial period. The way to know if the Millennium 2.0 Hybrid is right for you is to lie on it in your own sleeping position at one of our Kentucky showrooms before you buy.
Can I see this mattress in person?
Yes. It is on the floor at our Kentucky showrooms, where you can lie on it directly next to firmer options in the Sierra Sleep lineup and feel the difference in your own sleeping position before deciding.
What sizes does it come in?
Twin XL, Full, Queen, King, and California King.
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.
