Abstract: The invention relates to a sleeve provided for protecting a timber pole against sub-soil decay. The application of the sleeve on a pole forms part of a primary/preventative form of treatment, the sleeve comprising a composite structure including at least two layers of synthetic plastic material. At least one of the layers of the sleeve has heat shrink properties permitting the sleeve to be heat shrunk onto a pole, all the individual layers of the sleeve being of different materials having different properties that are selected in terms of the specific conditions of a pole to be protected and the sub-soil conditions to which the pole will be exposed, in use.