Buy Cheap Box Spring -

Amazon Basics Smart Box Spring (~$80–$100). This all-steel foundation is highly rated for ease of assembly. Note that it has a weight limit of 350 lbs, making it better for solo sleepers or children rather than heavy couples.

If your slats are more than 4 inches apart, your mattress may sag into the gaps. Look for "mattress foundations" with more slats if you have a heavy foam bed. buy cheap box spring

Zinus WonderBox / Smart Box Spring (~$70–$110). It features a steel frame that snaps together without tools. Reviewers praise its silence and durability, though some note it can run slightly narrow for certain mattresses. Amazon Basics Smart Box Spring (~$80–$100)

Standard box springs are 9 inches, while "low-profile" ones are 5 inches. Measure your current bed height to ensure your mattress doesn't end up too high. If your slats are more than 4 inches

Box Spring vs Platform Box: Shopping Advice - Bedrooms & More