Cuprinol Ultimate Wood Preserver (BP) works in three ways to colour and protect rough sawn and smooth planed garden wood|It penetrates deep into wood to protect against rot, decay and mould growth|Special colourfast pigments give rich natural shades that resist fading and bleaching for up to 5 years (smooth planed wood may require more regular treatment)|Water repellent waxes and resins help prevent rain penetration whilst allowing the wood to breathe, resisting cracking and flaking