A component, such as a blade, vane or combustor wall of a gas turbine engine comprises two walls defining a coolant passage and has an array of pedestals extending between the two walls for heat removal. Each pedestal changes in cross-section along its length. Alternate rows of pedestals are arranged such that their larger cross-sectional area is adjacent one wall then the other. When a coolant flows through the passage it is forced to flow between one wall and the other wall so as to increase turbulence and hence mixing for a more even coolant temperature. The array of pedestals can also be used to tailor the individual heat loads on each wall independently and has the ability to use differing levels of blockage to counter adverse pressure gradients along successive rows of pedestals.