Mountain Air Organic Beds™ zippered casings is made of Organic Cotton Knit cover. Our layers are made of organic latex and can be easily moved around to make it firmer or softer on each side, providing you the ultimate in sleep-surface customization. This is custom made for you as you may choose to change the density on your order to any combination of Firm/Medium/Soft on each side so each sleeper can have their own sleep surface. The organic cotton knit cover is a casing with a zipper that allows you to control the feel of your mattress instead of the mattress controlling you. You can now unzip your mattress and move layers around to adjust the feel. Even 5/10/15 years down the road you can control the comfort of your mattress. How awesome is that? If you choose to split the top layer, we recommend you purchase our Cool and Cozy quilted mattress protector. To make things extra nice we give you a hundred and twenty day free layer exchanges, this way you can adjust the feel for yourself so you're guaranteed your comfort. No one can really tell what they need to sleep on until they sleep on it for a few days. You can try out a sea of mattresses in a mattress store and you will never know for sure until you sleep on it whats best for you. Your body will tell you what you need, this is why what we do is so important for your comfort. Please call us for a personalized recommendation for each sleepers needs as we have had over 11 years experience helping people choose the best mattress for them based on their individual needs. We have helped people from rheumatoid arthritis, fibromyalgia, to completely fused spines. If we can do that for them, imagine what we can do for you. Call us today and let us guide you to a life changing mattress you will love the rest of your life.