A pre-diffuser of a gas turbine engine, comprising: an air passage bounded by an inner diameter wall, an outer diameter wall, a first strut and an annularly adjacent second strut; each strut including: a forward edge defining a leading edge, characterised by: an upper contour with an upper contour forward end, which has a larger upper contour first radius, and an upper contour aft end, which has a smaller upper contour second radius that is smaller than, and located aft of, the larger upper contour first radius, wherein the upper contour includes a straight and linear section with a radius value equal to infinity; a lower contour, that differs from the upper contour, with a lower contour forward end, which has a larger lower contour first radius, and a lower contour aft end, which has a smaller lower contour second radius that is smaller than, and located aft of, the larger lower contour first radius; wherein both the upper contour and lower contour transition from parallel to airflow, to perpendicular to airflow, defining a gradual airflow transition from the parallel, with respect to airflow, outer diameter wall to the perpendicular portion of the leading edge provided by the larger upper contour first radius that smooths an airflow through the air passage and reduces internal drag losses. an air passage bounded by an inner diameter wall, an outer diameter wall, a first strut and an annularly adjacent second strut; each strut including: a forward edge defining a leading edge, characterised by: an upper contour with an upper contour forward end, which has a larger upper contour first radius, and an upper contour aft end, which has a smaller upper contour second radius that is smaller than, and located aft of, the larger upper contour first radius, wherein the upper contour includes a straight and linear section with a radius value equal to infinity; a lower contour, that differs from the upper contour, with a lower contour forward end, which has a larger lower contour first radius, and a lower contour aft end, which has a smaller lower contour second radius that is smaller than, and located aft of, the larger lower contour first radius; wherein both the upper contour and lower contour transition from parallel to airflow, to perpendicular to airflow, defining a gradual airflow transition from the parallel, with respect to airflow, outer diameter wall to the perpendicular portion of the leading edge provided by the larger upper contour first radius that smooths an airflow through the air passage and reduces internal drag losses. a forward edge defining a leading edge, characterised by: an upper contour with an upper contour forward end, which has a larger upper contour first radius, and an upper contour aft end, which has a smaller upper contour second radius that is smaller than, and located aft of, the larger upper contour first radius, wherein the upper contour includes a straight and linear section with a radius value equal to infinity; a lower contour, that differs from the upper contour, with a lower contour forward end, which has a larger lower contour first radius, and a lower contour aft end, which has a smaller lower contour second radius an upper contour with an upper contour forward end, which has a larger upper contour first radius, and an upper contour aft end, which has a smaller upper contour second radius that is smaller than, and located aft of, the larger upper contour first radius, wherein the upper contour includes a straight and linear section with a radius value equal to infinity; a lower contour, that differs from the upper contour, with a lower contour forward end, which has a larger lower contour first radius, and a lower contour aft end, which has a smaller lower contour second radius that is smaller than, and located aft of, the larger lower contour first radius; wherein both the upper contour and lower contour transition from parallel to airflow, to perpendicular to airflow, defining a gradual airflow transition from the parallel, with respect to airflow, outer diameter wall to the perpendicular portion of the leading edge provided by the larger upper contour first radius that smooths an airflow through the air passage and reduces internal drag losses.