A heat-recoverable closure assembly for enclosing e. g. cable splices comprising a heat-recoverable outer sleeve surrounding a body to be enclosed thereby, a support member surrounding the body and within the sleeve which support member has slotted end portions arranged to be capable of forming a tapering transition from the support member to the body, and a flexible barrier layer bridging the slots of the slotted portions. The barrier may act to seal the slots against ingress of moisture ior heat, and the barrier layer preferably covers substantially all of one surface of the support. Foamed polymer layers are particularly suitable as heat barriers, and metallic layers carried on a flexible carrier are particularly suitable as moisture barriers. The barrier may be inside or outside the support member, to suit end use requirements. A heat barrier will normally be placed outside the support member when the latter is made of thermoplastic material.