3" Extra Firm Rubber Core 16 x 80" for use to convert your Zippered Queen Mattress into a Zippered King Mattress and prevent one from needing to buy a whole new mattress. All you need is the Conversion Core(s), an extra soft 3" or 2" king core if nessessary, and a King Zip Outer that matches your mattress depth and you are ready to go.
