Mattress foundations are available in the standard 9" height as well as the low profile 5.5" height.

*King foundation price is for a complete set. 

Which one should you choose?

The standard 9" box foundation is the typical size in most mattress sets.  However, many mattresses today are much taller so if you are ordering a taller mattress and don't want your overall bed height too tall you might consider the Low Profile box foundation.