A disc for a gas turbine engine, the disc comprising: a disc hub (203; 403; 603) comprising an interstage coupling (207; 307; 407; 607); a disc web (202; 602) that extends radially outward from the disc hub, relative to an axis of rotation of the gas turbine engine; a disc blade attachment (204; 604) connected to the disc web (202; 602) at an end of the disc web opposite the disc hub (203; 403; 603), wherein the disc blade attachment extends radially outward, wherein the disc blade attachment is configured to attach an airfoil (222; 622) to an upper surface of the disc blade attachment; and a cover plate (206; 406; 506; 660) that extends from the disc blade attachment radially along an outside surface of the disc web toward the disc hub creating a cavity between the cover plate and disc web; wherein the interstage coupling (207; 307; 407; 607) is disposed on an axially extending surface at a peripheral aft edge of the disc hub that includes a protrusion that extends axially in the aft direction beyond an aft surface of the disc hub; the disc hub comprises: a groove (233; 333; 533; 633) formed on the axially extending surface (212; 312; 412; 612) of the disc hub, wherein the groove includes a forward surface (213; 313; 413; 513; 613) that extends radially into the disc hub to a groove floor (214; 314; 414; 514; 614) that is cut into the disc hub and extends axially to an aft surface (216; 316; 416; 516; 616) that extends radially outward to at least the axially extending surface of the disc hub; and a scallop (520; 521) formed along at least one surface of the groove, wherein the scallop is configured to provide a flow path; and a retaining ring (210; 310; 510; 610) is configured to engage with the groove (233; 333; 533; 633) between the cover plate (206; 406; 506; 660) and disc, wherein the retaining ring connects to the interstage coupling (207; 307; 407; 607) of the disc hub and extends into the groove. a disc hub (203; 403; 603) comprising an interstage coupling (207; 307; 407; 607); a disc web (202; 602) that extends radially outward from the disc hub, relative to an axis of rotation of the gas turbine engine; a disc blade attachment (204; 604) connected to the disc web (202; 602) at an end of the disc web opposite the disc hub (203; 403; 603), wherein the disc blade attachment extends radially outward, wherein the disc blade attachment is configured to attach an airfoil (222; 622) to an upper surface of the disc blade attachment; and a cover plate (206; 406; 506; 660) that extends from the disc blade attachment radially along an outside surface of the disc web toward the disc hub creating a cavity between the cover plate and disc web; wherein the interstage coupling (207; 307; 407; 607) is disposed on an axially extending surface at a peripheral aft edge of the disc hub that includes a protrusion that extends axially in the aft direction beyond an aft surface of the disc hub; the disc hub comprises: a groove (233; 333; 533; 633) formed on the axially extending surface (212; 312; 412; 612) of the disc hub, wherein the groove includes a forward surface (213; 313; 413; 513; 613) that extends radially into the disc hub to a groove floor (214; 314; 414; 514; 614) that is cut into the disc hub and extends axially to an aft surface (216; 316; 416; 516; 616) that extends radially outward to at least the axially extending surface of the disc hub; and a scallop (520; 521) formed along at least one surface of the groove, wherein the scallop is configured to provide a flow path; and a groove (233; 333; 533; 633) formed on the axially extending surface (212; 312; 412; 612) of the disc hub, wherein the groove includes a forward surface (213; 313; 413; 513; 613) that extends radially into the disc hub to a groove floor (214; 314; 414; 514; 614) that is cut into the disc hub and extends axially to an aft surface (216; 316; 416; 516; 616) that extends radially outward to at least the axially extending surface of the disc hub; and a scallop (520; 521) formed along at least one surface of the groove, wherein the scallop is configured to provide a flow path; and a retaining ring (210; 310; 510; 610) is configured to engage with the groove (233; 333; 533; 633) between the cover plate (206; 406; 506; 660) and disc, wherein the retaining ring connects to the interstage coupling (207; 307; 407; 607) of the disc hub and extends into the groove.