The core of Saplings Cool Flow Spring Cot Bed Mattress is made from a high quality mini-bonnell spring unit. This is encased in high density quality foam and is then covered with an anti-allergenic special cover. The advantage of this core is that it provides long term resilience and support at the same time providing a comfortable sleeping environment due to its spring construction. This is a special anti allergenic 5 layer material which is designed to be an effective barrier to dust mite allergens and is 99.9 efficient. The soft and lightweight material This cot bed mattress is superbly breathable and allows body heat to be dissipated effectively making Saplings Cool Wave cot bed mattress an extremely comfortable and safe baby mattress to sleep on. The cover is removable for washing. The topper pad of Saplings Cool Flow Spring baby mattress is designed to give extra comfort with the additional benefit of being removable and easy to wash. It is attached by a zip to the cot bed mattress and is made from the same anti-allergenic material with a polyester infill. All Cool Wave mattress covers and mattress toppers are machine washable at 60degrees which is the temperature to kill house dust mite allergen. In addition, the mattress cover can be wiped with a damp cloth to clear the surface of allergens.