A pipe insulating section (1) comprises a generally cylindrical hollow phenolic foam body (2) of substantially uniform cross section with an inner facing web (3) and an outer facing web (4). The phenolic foam body (2) is slit longitudinally to provide section halves which can be opened to facilitate wrapping around a pipe to insulate the pipe. The section halves are linked by the outer web (4) at one side and facing ends of the section halves at the other end are faced with the inner facing web (3). The inner web (3) may be of paper and the other web (4) may be of an aluminum foil. An apparatus used in manufacturing the elongate shaped phenolic section comprises an outer mould (10) for forming the outer facing (4) into a cylindrical shape and an inner mandrel (11) for forming the inner facing (3) into a cylindrical shape, which is of smaller diameter than that of the cylinder defined by the outer facing (4). The facings (3, 4) define a hollow core therebetween into which liquid foam reactants (20) are injected through an injector (25).