Please note that even this is a dual madras, you only put one madras in the cart at a time! A hardside water mattress has straight cut sides and unlike the softside water mattresses it is not placed in a foam frame. The water mattress is made of phthalate free vinyl, and the materials used are OEKO-TEX100 certified. On your present water mattress you can read more about your mattress type and level of stabilisation.