This invention relates to coverings for structural members to provide passive fire protection. An assembly comprises an elongate structural member; a pre-cast casting disposed around the structural member comprising an elongate heat insulating tube and a support tube. The elongate heat insulating tube being made of a heat insulating material providing passive fire protection, and the heat insulating tube having a continuous inner circumferential surface and a continuous outer circumferential surface. The support tube being encapsulated within the heat insulating tube between the inner circumferential surface and the outer circumferential surface. A stabilising element is arranged to maintain a gap between the inner circumferential surface of the heat insulating tube and an outer surface of the structural member.