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Serta

Serta Perfect Sleeper X Knox Firm Innerspring 13.5" Twin XL Mattress

(0) Reviews KNOXFM3/3XLMATT
Sale Price $999.00 Save $200 $799.00 + Free Delivery
Size:
King California King Queen Full Twin XL
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Serta Perfect Sleeper X Knox Firm Innerspring 13.5" Twin XL Mattress

Sale Price $999 Save $200 $799
Add to Cart
0% APR with equal monthly payments of $34/mo. for 24 months
or Buy Now, Pay Later. No ongoing commitment.

Benefits

  • Motion Separation
  • Temperature Regulation

Explore Serta® Perfect Sleeper X Knox Firm Innerspring 13.5" Mattress

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Description

Serta® Knox Firm Mattress

Experience dependable support and lasting comfort with the Serta® Knox Firm mattress—crafted for sleepers who prefer a firmer, more supportive feel. Designed to keep your body properly aligned, the Knox Firm delivers consistent comfort with minimal sink, helping you wake up feeling refreshed and supported. Serta® Individually Wrapped Coil Technology adapts to your movements while reducing motion transfer, making it ideal for shared sleep. Firm Serta® Comfort Foam layers provide a supportive sleep surface that resists sagging and promotes healthy spinal alignment. Topped with a breathable knit cover, the Knox Firm delivers a cool, stable, and supportive sleep experience night after night.

Individually Wrapped Coil Technology

Provides targeted support and limits motion transfer by allowing each coil to move independently.

Firm Serta® Comfort Foam

Offers a supportive, responsive feel that helps maintain proper alignment without excess softness.

Firm Comfort Feel

Ideal for back and stomach sleepers or anyone who prefers a more stable, supportive surface.

Breathable Knit Cover

Enhances airflow and provides a clean, comfortable sleep surface.

Stable Foam Base Layer

Creates a durable foundation that supports the coil system and extends mattress longevity.

Specifications

Type
Innerspring

Comfort
Firm

Brand Serta
Mattress Type Innerspring
Size Twin XL
Height 13.50"
Width 39.00"
Depth 80.00"
Weight 66.26 lbs
Warranty 10 Year Limited
Profile Height 13.5"
Works With Adjustable Base? Yes
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Serta® Perfect Sleeper X Knox Firm Innerspring 13.5

Serta® Perfect Sleeper X Knox Firm Innerspring 13.5" Mattress

Serta® Perfect Sleeper X Knox Firm Innerspring 13.5" Mattress
Customer Reviews (0) Reviews

Need Help Choosing a Mattress?

The mattress experts at Gardner White have your back! Our Mattress Buying Guide can help you cut through all the confusion when you're shopping for a new mattress. Decades of collective experience went into creating the perfect guide for mattress shopping, check it out now!

We've also developed a list of the Best Mattresses of 2025. These include the Best Innerspring Mattress, the Best for Back Pain, and the Best Cooling Mattress among ten other 'Best Of' models. If you're looking for the best of the best in a new mattress, this list is your go-to guide to find youre perfect fit!

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