Plan each side of a split bed.

Separate mattresses, split-head designs and independently moving sides need different checks. Start with the configuration you actually own.

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Start with the component you need

What are you trying to fit?Where are you shopping?Measurement units

Measure the area to cover

Width (in)Length (in)

Finished stack height (including topper) (in)I measured these dimensions; they are not just a size label.

Base typeMattress arrangement

Material exclusions (optional)

Exclude latex

Incomplete material lists remain unverified. Do not use this tool as allergy certification.

Movement and manufacturer checks

Movement neededFitted sheet / protector arrangementExact mattress/base approval

Slat and support checks

Actual gap between slats (in)Manufacturer maximum slat gap (in)I checked load, slat, center-support and attachment requirements in both manuals.

Two base sections do not necessarily mean independent movement. Split-head and fully split mattresses require different fitted coverings. For two sides with different heights, run this check twice.

Two separate mattresses or a split head?

A US split king commonly uses two 38 × 80 inch mattresses. A joined split-head mattress is a different shape. Sleep Number describes its FlexTop King as independently moving head sections with a lower half that moves together. The label “king” does not make these coverings interchangeable.

Worked example: for two 38 × 80 × 12 inch sides, the Avocado standard Twin XL protector has matching stated dimensions and a 6–16 inch fit range. Check each side separately. A single 76 × 80 fitted protector spanning both sides restricts independent movement; a shared flat sheet is a separate choice and can still pull. Exact base approval remains a separate check.

Confirm mattress model, base model, movement zones, attachment requirements, support limits and covered heights. Never infer approval from flexible foam. Keep functional components while resolving missing documentation.

Sleep Number configuration definitions and support specifications

Before a purchase, recheck the exact model, size and pocket version. Confirm care instructions and the actual seller’s return terms, including opened bedding. Direct-brand terms do not automatically apply to another retailer.

See the manufacturer dimensions and fit ranges →

Read the compatibility methodology · Report a specification correction