King Koil Mattress

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King Koil SmartLife Mattress in Las Vegas and St. George, UT

The King Koil SmartLife Lily Medium memory foam mattress combines firm support with plush comfort to deliver an incredible sleeping experience night after night.

Body Sensing Technology

Thanks to the SmartLife body sensing technology, the high-density mattress adapts to your body’s unique shape. The contouring mattress ensures optimal comfort all night. Meanwhile, the HypurGel top layer matches your movements to deliver a better quality sleep.

SmartLife App for Premium Relaxation

Alternatively, when linked to the SmartLife App, the mattress’s Relaxation Mode enables you to enjoy a top to toe massage. It brings spa-like massage directly to your home on a daily basis. Moreover, the premium quality foam encasement is sure to maintain those winning attributes for 25 years or longer.

A Royal Mattress Brand

King Koil is one of the most reputable brands in the beds and mattresses industry. The SmartLife Lily Medium will ensure that your bed is fit for royalty.

King Koil SmartLife Mattress Sizes

The 12” mattress is available in queen, king, or California king sizes. It’s an excellent choice for couples of all sizes. Parents will enjoy the little extra space for when the kids sneak in during the early hours.

120-Day Comfort Guarantee & Shipping

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In-stock merchandise purchased by 1 pm will be delivered the same day upon request, excluding holidays and limited to a geographic area with a minimum purchase of a $599 mattress set. Excludes floor models. See store for details.


The room must be ready for delivery when the drivers arrive.

As a service, we will remove your old mattress and box spring before delivering the new set (subject to inspection, unsanitary bedding will not be removed, limited to equal amount delivered).

As a service, we will remove your old mattress and box spring before delivering the new set (subject to inspection, unsanitary bedding will not be removed, limited to an equal amount delivered).

Delivery cannot be made to a minor and finance orders will require a signature from someone with a valid state-issued ID.

The driver will call the phone number provided on your order on the morning of delivery to give you a three-hour time frame. If you are not home for a delivery, there will be a $69.99 re-delivery fee.

If the driver determines that the delivery attempt could cause damage to your home, you will be required to sign a release of liability to complete the delivery.

Our C.O.D. Policy:

All orders must be paid in full before the delivery date. We do not accept payment at the time of delivery.

10-Year Limited Warranty

Beautyrest stands by its products and materials with limited warranties so you rest easy.

Our-120 Day Sleep Guarantee

If you have owned your mattress for longer than 30 days and you aren't happy with your set, Best Mattress is glad to exchange your mattress for 120 days from the date of purchase. Please see our full terms & conditions here.

Best Mattress also offers FREE REMOVAL* of your old mattress. Our delivery driver will pick up your old mattress and seal it in plastic before loading it onto our truck.

Need financing? We have you covered! Best Mattress offers a variety of options available, including No Credit Check Financing! Please contact us for additional details on all offers.

We appreciate your patience, understanding, and support at this time. Thank you for continuing to be a loyal Best Mattress customer. Sleep Easy, Friends!

Available Bed Sizes

See our mattress sizes and dimensions page.

Twin Bed

39″ X 75″

Twin XL Bed

39″ X 80″

Full Bed

54″ X 75″

Queen Bed

60″ X 80″

King Bed

76″ X 80″

California King Bed

72″ X 84″