Our Pure-Rest Sagittarius pure natural rubber mattress has 5.5-6 inch pure chemical-free natural rubber core and a 3" natural rubber soft topper, which is then surrounded by organic cotton fabric layer, with organically processed wool from organically raised sheep quilted to our deluxe Pure-Rest European organic cotton fabric which ensures the wool will not migrate out over the years. The quilting prevents shifting and provides a sturdy durable, and comfortable sleeping surface. Our extra amount of wool make the top more comfortable than other manufacturers who tend to use a little less on top to cut costs. These mattresses easily conform to your body's shape and minimizes pressure on your joints and back. Highly recommended by chiropractors for back support without the uneven support such as all innerspring mattresses have. Customize your support and your firmness. The 6" core of any type of mattress is your support, If you put a topper or a latex overlay about 2-3" thick, you will not affect support, this only affects your comfort. We chose to make this system as it is affordable and supportive. The layered beds with more than 2 layers seem to often have problems of breaking down (if the individual layers are not covered to prevent scraping against each other). Choose your support core, default is FIRM. Medium (25-30 ILD recommended for children) FIRM (35-38 ILD most prefer this) ExtraFIRM (42-45 ILD for overweight persons or those who prefer a really firm feel) You may also place this style mattress on a slatted bed, like our Pacific Rim Beds in the furniture section.