An airfoil comprising: pressure and suction side walls extending in a chord-wise direction (C) between leading and trailing edges , the pressure and suction side walls extending in a radial direction (R) to provide an exterior airfoil surface ; a core cooling passage arranged between the pressure and suction walls in a thickness direction (T) and extending radially toward a tip ; a skin passage arranged in one of the pressure and suction side walls 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 , and the core cooling passage and the skin passage are configured to have a same direction of fluid flow (F); and a resupply hole which fluidly interconnects the core and skin passages 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 (G) relative to the direction of fluid flow (F) in the core cooling passage , the acute angle (G) lying in a plane parallel to the thickness direction (T); a skin passage height (H) 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 extending in a chord-wise direction (C) between leading and trailing edges , the pressure and suction side walls extending in a radial direction (R) to provide an exterior airfoil surface ; a core cooling passage arranged between the pressure and suction walls in a thickness direction (T) and extending radially toward a tip ; a skin passage arranged in one of the pressure and suction side walls 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 , and the core cooling passage and the skin passage are configured to have a same direction of fluid flow (F); and a resupply hole which fluidly interconnects the core and skin passages 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 (G) relative to the direction of fluid flow (F) in the core cooling passage , the acute angle (G) lying in a plane parallel to the thickness direction (T); a skin passage height (H) 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 (G) relative to the direction of fluid flow (F) in the core cooling passage , the acute angle (G) lying in a plane parallel to the thickness direction (T); a skin passage height (H) 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. <EOS>