A sleeve, which finds particular application in the environmental sealing of joints between insulated pipes, comprises heat-recoverable polymeric sheet material provided at separate regions of a principle surface thereof with a layer of a heat-activatable adhesive for bonding the sheet to the pipe insulation, and a layer of a sealant to accommodate flexibility in the joint. A layer of a sealing material, having an elongation modulus greater than that of the sealant, overlies at least part of the sealant layer, to improve the pressure retention properties of the sleeve.