Low profile box springs, or foundations, were created as an alternative to regular height versions. Adding a low profile foundation to your mattress lowers the overall height of the bed. Mattress manufacturers have been creating taller and taller mattresses in the last few years. A low profile foundation typically measures 4-5 inches whereas a regular foundation is 9 inches or more. This is a big help when your mattress can measure as tall as 18 inches.
The most thin box spring you can get is the ultra low profile box spring, just 2 inches tall, it may also be called a bunkie board. If you’re not looking to add height and you just want support, it’s pretty much a flat box spring that will just provide a supportive surface for your mattress.
Most mattress manufacturers produce low-profile box springs that match the new mattress that you're buying, so you can get the best low profile box spring for your needs. In most cases, the warranty for your mattress requires that you pair it with a foundation. A low-profile foundation is just as supportive as a standard-sized box spring. To find out if you need one, read: Do I Need a Box Spring?