The zipper is the difference:

Do It Yourself has become a trend that has taken off within recent years . Everything from cleaners to furniture can be done right in the comfort opf your home and often cost less than their commercial counterparts.  What if there was a way to craft your perfect mattress without having to spend thousands?  There are so many mattress combinations available now that it can be hard to know which mattress is right for you, especially if you and your partner have different comfort levels and sleeping positions.  A DIY mattress can be your ideal match. Follow our guide to build the mattress of your dreams

We have compiled alphabetical list of most advertised online “Bed in a Box” models, and the components used to build them. You can use these models as guidelines to build your “Copycat” DIY mattress. Your DIY mattress will never be an exact duplicate, but it will be so close, we challenge you to feel the difference.

All DIY mattresses have the unique benefit of a zipper cover.  This allows you to open the mattress, and add or rearrange the comfort layers inside.  This design is far superior to the Bed in A Box mattresses that lack the benefit of “In Home” adjustability.