Abstract: An enclosure (1) around a substrate (3) such as a telecommunications cable is made pressure retaining by the provision of re-entrant seals (5), generally V-shaped in cross-section, that are positioned at the region where the enclosure is bonded (4) to the substrate pressure within the enclosure thus tends to open the V rather than put the bond in peel. The re-entrant seals may be cut-to-length in the field and a leak path through the resulting open end (23) avoided by using pressure (P) within the enclosure to close the open end or to balance pressure across it.