The Sleeve is made of robust RPET material which perfectly adapts to the form of the notebook like a second skin. The best guaranty against surface scratches and other dents and damages. The design is not only robust, but also extremely light. The notebook can thus be transported flexibly without taking up a lot of space in your bag. Another advantage: The zipper is fitted with an extra surface on the inside in order to avoid scratches on the notebook. The ONE series emphasises the durability of the product with an extended five year guarantee - and they are all using recycled PET main material!