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Zinus

Zinus 4 Inch Box Spring with Cover, No Assembly Mattress Foundation, Sturdy Metal Structure, Split Cal King, White

  • Based on 7,287 reviews
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Size: Split California King


Pattern Name: Box Spring


Features

  • Sturdy Steel Frame With Poly Jacquard Cover
  • AS SIMPLE AS UNFOLD & UNWIND - Requiring no tools and zero tedious assembly, the innovative No Assembly box spring requires only unfolding to become bedtime ready; the hardest part will be taking it out of the box.DURABLY ENGINEERED - Durable steel is used to construct the interior framework of this reliable foundation; twin size supports a maximum weight capacity of 350 lbs, while all other sizes can support up to 700 lbs; King and Cal King sizes are split versions
  • LOW PROFILE DESIGN - A 4 inch height is perfect for taller mattresses or for those who enjoy their bed lower to the floor
  • THOUGHTFULLY PACKAGED - All parts and instructions are packed into one compact box that ships straight to your door
  • Worry-free 5 year limited warranty included; box spring only, a bed frame or platform bed is required to support this foundation and is sold separately

Description

Believe it or not, we’ve made the box spring more functional, more durable, and dare we even say, fun! Our No Assembly Box Spring is not your average foundation. Its folding design not only makes set-up insanely easy, but it also comes in handy on moving day, maneuvering easily in and around tight hallways and corners. What’s more, it features a structure made of thick and durable steel, meaning that frames and mattresses may come and go, but this box spring will be with you for the long haul. Once unboxed, this brilliant foundation practically assembles itself by taking shape once unfolded. Essentially, deciding where to place the bed will take longer than setting up this box spring. Backed by both our 5-year worry free warranty and hundreds of positive customer reviews, this box spring is about as easy as decisions get.

Brand: Zinus


Size: Split California King


Product Dimensions: 83"L x 71.5"W x 4"Th


Item Weight: 49.9 pounds


Item Firmness Description: Medium


Top Style: Tight Top


Cover Material: Polyester


Number of Layers: 1


Fill Material: Memory Foam


Weight Limit: 700 pounds


Item Firmness Description: Medium


Number of Layers: 1


Weight Capacity Maximum: 700 pounds


Additional Features: Sturdy


Mattress Coil Type: Continuous Coil


Construction Type: Steel Frames


Number of Mattress Coils: 1


Mattress Base Compatibility: Box Spring


Size: Split California King


Item Dimensions L x W x Thickness: 83"L x 71.5"W x 4"Th


Item Weight: 49.9 pounds


Item Thickness: 4 inches


Item Depth: 4 inches


Item Dimensions: 83 x 71.5 x 4 inches


Cover Material: Polyester


Fill Material: Memory Foam


Mattress Comfort Layer Material: Memory foam


Material Type: Fabric, Steel


top-style: Tight Top


Color: White


Style Name: 4 Inch


Brand Name: Zinus


Model Name: No Assembly Metal Box Spring


Product Benefits: Easy setup, durable, and maneuverable box spring


Model Number: OLB-BIFD-4CK


UPC: 841550091786


Number of Items: 1


Global Trade Identification Number: 86


Manufacturer: Zinus


Manufacturer Warranty Description: Worry-free 5 year limited warranty included.


Unit Count: 41.21 Square Feet


Age Range Description: Adult


Included Components: Box Spring


Item Type Name: Box Spring


Manufacturer Part Number: OLB-BIFD-4CK


Set Name: California King


Frequently asked questions

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View our full returns policy here.

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Similar Products

Top Amazon Reviews

    • Well Worth the Upgrade
Size: Split King Pattern Name: Box Spring
I was hesitant at first to pay more for this box spring when there were cheaper options, but after using it, I can confidently say it was worth it. Setup was incredibly easy—it took less than five minutes to get it out of the box, remove the packaging, unfold it, and have the bed fully set up. No tools, no assembly, no frustration. If you’ve ever struggled with a traditional box spring, this is a game changer. The bifold design also makes it easy to maneuver through tight spaces. The 4‑inch low profile gives the bed a clean, modern look and works perfectly with thicker mattresses. The steel construction feels noticeably sturdier and higher quality than other box springs I’ve owned—no creaking, no shifting, and it feels built to last. For a Split King, this is an excellent option and far easier to handle than a single bulky foundation. Bottom line: While it costs a bit more upfront, the ease of setup and superior quality make this a smart purchase. Practical, well‑designed, and exactly as described. Highly recommend. ... show more
Reviewed in the United States on March 24, 2026 by Amber Jaarda
    • Amazing product!!
Size: Split King Pattern Name: Box Spring
The design of this box spring is ingenious! It shows up in a box that is much smaller than you expect for a king size. It is lightweight and requires no assembly! Looks like it’s made extremely well and fit perfectly!
Reviewed in the United States on August 26, 2026 by J. Buckley
    • Noise Free
Size: Split King Pattern Name: Box Spring
I am a 62 year old woman, I took on the task of setting this up by myself and I successfully did! It was a little heavy but I used my furniture movers to help move it . It ig for my guest room for guests who had trouble getting in and out of the tall bed. Also my dogs enjoy getting on the bed to nap easier. It took me half hour to get it all done since my dogs were with me, otherwise I think I could have finished in 15 to 20 minutes. It's easy to set up just unfold it. Outside of the size and weight of removing from the box and setting up. It is sturdy and more than worth the price. It fit my king mattress perfectly. Thanks to no springs it is noise free. Hmm. I think I'll go take a nap. 😴 ... show more
Reviewed in the United States on November 18, 2025 by Cindy
    • Excellent product, works well, easy set up.
Size: Queen Pattern Name: Box Spring
Review Image by carol
Review Image by carol
Review Image by carol
Review Image by carol
Review Image by carol
Review Image by carol
I am a 56 year old woman and I was able to set this up all by myself. It was definitely a bit awkward and heavy-ish. It was not the easiest thing to do without a second person helping, but it is doable. The whole process (from box to finished with bedspread back on the bed) was about 20 minutes. There's nothing to it in terms of set up, other than the awkwardness of wrestling it out of the carton (it's kind of heavy), getting your mattress off the bed by yourself, wrestling the box spring onto the bed by yourself and then putting your mattress back on top by yourself. Once you get it out of the carton and you unfold it, the box spring "springs" to life. There is no assembly required other than unfolding it. It is for a guest bedroom so I haven't had any reports yet from guests sleeping on it. It looks sturdy and the perfect height for my platform bed. It has a much more inviting look now and will be easier for older guests to get in and out of the bed now. I didn't want a full height box spring because that would have been too high. This is perfect. I compared this against the least expensive Queen box spring I could have gotten delivered from a local mattress store and I saved over $100.00 overall (once you figure in $59 for white glove delivery, sales tax and the higher price for the box spring). I am very pleased with the purchase! The pictures I have attached show the process from box to finished bed. You can also compare how low my bed looked before versus how nicely elevated it is after adding the box spring. ... show more
Reviewed in the United States on February 15, 2017 by carol
    • Perfect Box Spring
Size: Queen Pattern Name: Box Spring
I needed a cheap and easy box spring for my new bed and this is it! its worth the money, easily to assemble, sturdy, and love that it folds!!!! which will come in handy whenever i move to take up less space
Reviewed in the United States on April 2, 2024 by Jaclyn
    • Sturdy, Easy to Use, and Works Great!
Size: Queen Pattern Name: Box Spring
Review Image by dugroz
Review Image by dugroz
Search for my username on YouTube (dugroz) and you can see my review/unboxing of the product. This low-profile foundation does exactly what it says it is supposed to do, and does it very well. It comes in a fairly large box and is a bit heavy, so an elderly or frail person would likely need help. However, once it is unboxed, there is no assembly needed, just unfold it, flip it over, and zip it up. (As others said, if you flip it open in the instinctive way, you need to flip it over.) It would be very easy to take with you in a move. This is not a "Box of Springs" - there are no springs inside. 95% of modern mattresses do not need a true "box spring" anyhow so that's fine. The purpose is just to raise up your mattress. It does not soften the mattress, nor is it designed to. "Foundation" is the better name. The bars are about 1/4 inch thick, and about 3 inches apart. The Foundation (as I measured it) was almost exactly 4 1/4" high (no big deal for me, but just noteworthy if you need "exactly" 4 inches in height). I was a bit Leary about using this with my Hybrid mattress since I was afraid that (because the bottom is foam) it would sink through. However, I emailed the mattress company and they assured me that this foundation is fine to use (I have a Sapira mattress). About 3 weeks of use so far, it's holding up fine, and the mattress works very well with it. Very sturdy, no sagging. No noise, no squeaking. We have a queen and it supports two grown adults just fine (the paperwork that came with it says that the queen size and up can support 2,400 lbs. of weight, which seems a bit ridiculous (2 people plus mattress weighing 2,400 lbs???), but the idea is that it is sturdy. . The sides are a nice patterned white cloth. Nice enough that we have not felt the need to cover it with a sheet like with did with our old one! I would recommend this foundation if 4 inches is the best height for your bed setup. Edit: 05/01/2017 - Still holding up great. ... show more
Reviewed in the United States on January 4, 2017 by dugroz
    • Box springs matter - and this one is awesome!
Size: Split California King Pattern Name: Box Spring
I just spent my first evening sleeping on this box spring. I want to provide a review because I am so impressed. First, this is a good that is well packaged. A lot of thought seems to have gone into how to make the package the smallest possible size, simple to move, simple to use, and overall well protected. I imagine that if someone believes they will move often then this is the absolute perfect box spring. I would like to contrast this with my previous "luxury" box spring. I have a California King bed. I purchased it through Hilton's Employee Program and used the box springs for 10 years. The box springs were nice, but large and nearly impossible to move effectively. When I moved internationally and then back to the USA this was a huge hassle. This Zinus 4-inch box spring set (approximately 1/2 the size/height of my previous "luxury" box spring) would be so much simpler to move. I would also like to point out that due to it being only 4 inches, my bed looks "normal" again instead of being slightly over 4 feet tall and difficult to get in/out of. Okay, so when the box is open the Zinus box spring is simple to set up. As in, under 30 seconds/ea. This was awesome. I expected to be screwing things together. Quality: Seems great! I believe these materials will last. It seems to be higher quality materials than the previous mattress box springs I had. Sleep: I slept so well last night! Big change from the previous box spring. I honestly thought box springs were not that big of a deal - it's about the mattress, right? - but this made a difference. My wife and I could tell immediately. Flat bed, comfortable, slept well, easy set-up, easy to move in the future, and we're happy campers! I highly recommend this box spring. ... show more
Reviewed in the United States on December 20, 2016 by J. Taillon
    • 5 Minutes
Size: Queen Pattern Name: Box Spring
This. This box spring is everything. Once I had taken my old box spring off, it took me about five minutes to open the box, remove bubble wrap, open and place this low profile box spring on my bed frame. I had no help, just me with my kid watching me, silently judging me for deciding to do the box spring switch during the middle of the day during a heatwave in a bedroom that doesn’t have AC. She was grilling me hard, or maybe I was projecting. Who knows?! Now, I carry a toddler around and am use to lifting heaven things with relative ease and found the frame much easier to navigate and lift than my queen foam mattress. The slats to the frame run vertically rather than horizontally which, is incredibly smart and, I believe, will create more support that lasts longer than the horizontal counterparts. The metal is sturdy and I noticed I’m not sinking as much as I did with my former wooden box spring that has larger spaces between slats. You don’t need to be superwoman set this up or a graphic design major from Sweden to decipher the directions. If you’re contemplating whether to get this boxspring, let this review be your sign to go ahead and treat yourself to some quality, easy to put together boxspring. You’re worth it. ... show more
Reviewed in the United States on August 7, 2022 by Elizabeth Wagner

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