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DuPont™ Tyvek® 2523B is a durable, water-resistant membrane that is reinforced with a laminated polypropylene nonwoven. This vapour-permeable membrane is extremely water-resistant and can be used for all supported and unsupported pitched roofs. For the placing on the market of the product in the European Union/European Free Trade Association (EU/EFTA) (with the exception of Switzerland) Regulation (EU) No. 305/2011 (CPR) applies. The product needs a declaration of performance taking into consideration EN13859-1: Flexible sheets for waterproofing – Definitions and characteristics of underlays - Part 1: Underlays for discontinuous roofing and EN 13859-2 Part 2: Underlays for walls. For the placing on the market of the product in the UK market the product needs UK Conformity Assessed (UKCA) marking supported by a UK Approved Body. For the application and use the respective national provisions apply.