A rotor (10, 210, 310, 410, 510) for use in a gas turbine engine, the rotor comprising: a wheel arranged around an axis; a first blade comprising a first material and extending radially outwardly away from the wheel relative to the axis to allow the first blade to interact with gases surrounding the rotor, the first blade having a first external surface (22, 222, 322) that defines a pressure side (36, 236, 336) of the first blade, and a second external surface (24, 224, 324) opposite the first external surface that defines a suction side (38, 238, 338) of the first blade, the first blade further having a leading edge (32, 232, 332), a trailing edge (34, 234, 334), and a first hole (42, 242, 342), wherein the first hole extends through the first external surface and into the first blade in a direction normal to the first external surface; and a first plug (18, 218, 318, 418, 518) located in the first hole and having a first outer surface (50, 250, 350) flush with the first external surface of the first blade such that the first outer surface is exposed to the gases surrounding the rotor, and the first plug comprises a second material that is different than the first material of the first blade; the rotor further comprising a second blade that extends radially away from the wheel and a second plug coupled with the second blade, the second blade directly neighboring the first blade circumferentially and having a first external surface that defines a pressure side of the second blade, and a second external surface opposite the first external surface of the second blade that defines a suction side of the second blade, the second blade further having a leading edge, a trailing edge, and a second hole, wherein the second hole extends into the second blade in a direction normal to the first external surface of the second blade, the second plug located in the second hole and comprising a third material that is different than the second material, characterized in that the second material has a density greater than a density of the first material and the third material has a density that is less than the density of the first material. a wheel arranged around an axis; a first blade comprising a first material and extending radially outwardly away from the wheel relative to the axis to allow the first blade to interact with gases surrounding the rotor, the first blade having a first external surface (22, 222, 322) that defines a pressure side (36, 236, 336) of the first blade, and a second external surface (24, 224, 324) opposite the first external surface that defines a suction side (38, 238, 338) of the first blade, the first blade further having a leading edge (32, 232, 332), a trailing edge (34, 234, 334), and a first hole (42, 242, 342), wherein the first hole extends through the first external surface and into the first blade in a direction normal to the first external surface; and a first plug (18, 218, 318, 418, 518) located in the first hole and having a first outer surface (50, 250, 350) flush with the first external surface of the first blade such that the first outer surface is exposed to the gases surrounding the rotor, and the first plug comprises a second material that is different than the first material of the first blade; the rotor further comprising a second blade that extends radially away from the wheel and a second plug coupled with the second blade, the second blade directly neighboring the first blade circumferentially and having a first external surface that defines a pressure side of the second blade, and a second external surface opposite the first external surface of the second blade that defines a suction side of the second blade, the second blade further having a leading edge, a trailing edge, and a second hole, wherein the second hole extends into the second blade in a direction normal to the first external surface of the second blade, the second plug located in the second hole and comprising a third material that is different than the second material, characterized in that the second material has a density greater than a density of the first material and the third material has a density that is less than the density of the first material.