A BOAS segment for a gas turbine engine, the BOAS segment comprising: a coolant supply surface configured to be in fluid communication with a coolant supply; a seal surface configured to be in fluid communication with a working medium fluid flow and arranged radially outward of a plurality of turbine blades; a first inter-segment surface extending between the coolant supply surface and the seal surface; a second inter-segment surface circumferentially offset from the first inter-segment surface and extending between the coolant supply surface and the seal surface; and an internal cooling passage between the coolant supply surface and the seal surface and extending between the first and the second inter-segment surfaces (31a, 31b) so as to be tapered, wherein the internal cooling passage comprises: a primary inlet aperture in fluid communication with the coolant supply and a first end of the internal cooling passage; and an elongated rib inside the internal cooling passage and proximate the primary inlet aperture; characterised in that the internal cooling passage comprises a first sidewall and a second sidewall and a first endwall and a second endwall connect the first sidewall and the second sidewall, and the elongated rib is connected to and partially extends from at least one of the first sidewall or the second sidewall toward another of the first sidewall or the second sidewall, wherein the elongated rib and the at least one of the first sidewall or the second sidewall are configured to direct at least a portion of the coolant from the primary inlet aperture against a proximate one of the first endwall or the second endwall of the internal cooling passage and then substantially reverse direction to flow downstream toward a second end of the internal cooling passage. a coolant supply surface configured to be in fluid communication with a coolant supply; a seal surface configured to be in fluid communication with a working medium fluid flow and arranged radially outward of a plurality of turbine blades; a first inter-segment surface extending between the coolant supply surface and the seal surface; a second inter-segment surface circumferentially offset from the first inter-segment surface and extending between the coolant supply surface and the seal surface; and an internal cooling passage between the coolant supply surface and the seal surface and extending between the first and the second inter-segment surfaces (31a, 31b) so as to be tapered, wherein the internal cooling passage comprises: a primary inlet aperture in fluid communication with the coolant supply and a first end of the internal cooling passage; and an elongated rib inside the internal cooling passage and proximate the primary inlet aperture; characterised in that the internal cooling passage comprises a first sidewall and a second sidewall and a first endwall and a second endwall connect the first sidewall and the second sidewall, and the elongated rib is connected to and partially extends from at least one of the first sidewall or the second sidewall toward another of the first sidewall or the second sidewall, wherein the elongated rib and the at least one of the first sidewall or the second sidewall are configured to direct at least a portion of the coolant from the primary inlet aperture against a proximate one of the first endwall or the second endwall of the internal cooling passage and then substantially reverse direction to flow downstream toward a second end of the internal cooling passage. a primary inlet aperture in fluid communication with the coolant supply and a first end of the internal cooling passage; and an elongated rib inside the internal cooling passage and proximate the primary inlet aperture; characterised in that the internal cooling passage comprises a first sidewall and a second sidewall and a first endwall and a second endwall connect the first sidewall and the second sidewall, and the elongated rib is connected to and partially extends from at least one of the first sidewall or the second sidewall toward another of the first sidewall or the second sidewall, wherein the elongated rib and the at least one of the first sidewall or the second sidewall are configured to direct at least a portion of the coolant from the primary inlet aperture against a proximate one of the first endwall or the second endwall of the internal cooling passage and then substantially reverse direction to flow downstream toward a second end of the internal cooling passage.