An airfoil comprising: pressure and suction side walls (86, 88) extending in a chord-wise direction between leading and trailing edges (82, 84), the pressure and suction side walls (86, 88) extending in a radial direction to provide an exterior airfoil surface; a core cooling passage (90a, 90b, 90c) arranged between the pressure and suction walls (86, 88) in a thickness direction and extending radially toward a tip; a skin passage arranged in one of the pressure and suction side walls (86, 88) to form a hot side wall and a cold side wall, wherein the hot side wall defines a portion of the exterior airfoil surface, the cold side wall defines a portion of the core cooling passage (90a, 90b, 90c), and the core cooling passage (90a, 90b, 90c) and the skin passage are configured to have a same direction of fluid flow; and a resupply hole which fluidly interconnects the core and skin passages (90a, 90b, 90c, 98) wherein the resupply hole has an exit at the skin passage, and the exit has a diffuser (118; 218; 318), characterised in that: a centerline of the resupply hole is arranged at an acute angle relative to the direction of fluid flow in the core cooling passage (90a, 90b, 90c), the acute angle lying in a plane parallel to the thickness direction; a skin passage height is in a range of 0.25- 5.08 mm (0.010-0.200 inches); the resupply hole comprises a metering section; and the skin passage has an aspect ratio that varies between 3:1 ≥ H/W ≥ 1:5, wherein H corresponds to the skin passage height and W corresponds to a skin passage width. pressure and suction side walls (86, 88) extending in a chord-wise direction between leading and trailing edges (82, 84), the pressure and suction side walls (86, 88) extending in a radial direction to provide an exterior airfoil surface; a core cooling passage (90a, 90b, 90c) arranged between the pressure and suction walls (86, 88) in a thickness direction and extending radially toward a tip; a skin passage arranged in one of the pressure and suction side walls (86, 88) to form a hot side wall and a cold side wall, wherein the hot side wall defines a portion of the exterior airfoil surface, the cold side wall defines a portion of the core cooling passage (90a, 90b, 90c), and the core cooling passage (90a, 90b, 90c) and the skin passage are configured to have a same direction of fluid flow; and a resupply hole which fluidly interconnects the core and skin passages (90a, 90b, 90c, 98) wherein the resupply hole has an exit at the skin passage, and the exit has a diffuser (118; 218; 318), characterised in that: a centerline of the resupply hole is arranged at an acute angle relative to the direction of fluid flow in the core cooling passage (90a, 90b, 90c), the acute angle lying in a plane parallel to the thickness direction; a skin passage height is in a range of 0.25- 5.08 mm (0.010-0.200 inches); the resupply hole comprises a metering section; and the skin passage has an aspect ratio that varies between 3:1 ≥ H/W ≥ 1:5, wherein H corresponds to the skin passage height and W corresponds to a skin passage width. a centerline of the resupply hole is arranged at an acute angle relative to the direction of fluid flow in the core cooling passage (90a, 90b, 90c), the acute angle lying in a plane parallel to the thickness direction; a skin passage height is in a range of 0.25- 5.08 mm (0.010-0.200 inches); the resupply hole comprises a metering section; and the skin passage has an aspect ratio that varies between 3:1 ≥ H/W ≥ 1:5, wherein H corresponds to the skin passage height and W corresponds to a skin passage width.