Bed Gap Filler for King Mattress - High-Density 45D Foam Fit

In this review the Deepshark bed gap filler is judged on fit, comfort and durability for king beds with a headboard gap. It is aimed at sleepers who want to stop pillows, remotes or small items falling between mattress and headboard and who prefer a simple, removable solution. The single biggest reason to consider it is the high-density 45D sponge core combined with a selection of sizes that aim to close the common 2 in to 12 in bed crack, so it performs as a practical mattress extender rather than a decorative cushion.

Key Features

• Broader size selection: Available for mattress widths including 78 in king, the filler comes in many lengths so it can match common mattress sizes and fill the gap accurately.
• High-density 45D sponge: The core uses resilient foam that resists collapse and provides a firmer barrier to keep pillows and small items on the bed.
• Wide application range: Designed for gaps at the headboard, between two mattresses, or against a wall, it converts a narrow gap into usable sleep space.
• Removable, washable cover: The breathable linen cover has a durable zipper that can be removed and machine laundered for easier cleaning.
• Compression packed: The filler ships compressed for transport and needs 48 to 72 hours to fully expand to its intended thickness.

Who It's For

The bed gap filler is best for owners of king or other standard mattresses who want a low-effort, physical barrier to stop items and pets from slipping into the headboard gap; its firm 45D sponge is a good match for sleepers who prefer a supportive, stable feel rather than a plush pillow. It is also appropriate for people who appreciate a washable cover to keep the sleep area tidy.

Those who should look elsewhere include buyers expecting an ultra-soft, pillow-like top or immediate full expansion out of the box; several buyers report the foam can take time to regain shape and sizing must be chosen carefully to avoid an incorrect fit.

Pros & Cons

Pros

• Sturdy, high-density foam core that maintains shape better than low-density fillers.
• Multiple size options allow a closer fit to mattress width and common bed crack sizes.
• Breathable, removable linen cover with zipper makes cleaning straightforward.

Cons

• Compressed packaging requires 48-72 hours to fully expand, so it may not appear full on delivery.
• Sizing must be chosen carefully; a few users reported receiving incorrect lengths that left the gap unfixed.

Specifications

Brand	DEEPSHARK
Core material	High-density 45D sponge
Cover material	Breathable linen fabric, removable with zipper
Intended use	Gap between mattress and headboard, mattress extender, wall edge, between mattresses
Available sizes	Fits mattress widths 39 in, 54 in, 60 in, 78 in; 64 total size options
Care	Removable cover; tumble dry low or air dry
Expansion time	Approximately 48-72 hours after unpacking

Our Verdict

The Deepshark bed gap filler is a practical, value-minded choice for anyone who needs a firm, washable solution to a headboard or mattress gap. With a resilient 45D sponge and many size options it fills the space reliably when the correct size is chosen, though buyers should allow a couple of days for full expansion and double-check dimensions before ordering.

Frequently Asked Questions

How long until the foam reaches full size?
The compressed foam normally needs about 48-72 hours to fully expand after unpacking.

Can I wash the cover?
Yes, the linen cover has a durable zipper and is removable; wash and tumble dry on low or air dry for best results.

Will this work between two mattresses?
Yes, it is designed for gaps between two mattresses as well as between mattress and headboard or wall; choose the size that matches your mattress width and gap depth.