The present invention relates to an integrally bladed rotor for use in a gas turbine engine. The integrally bladed rotor comprises a plurality of pairs of airfoil blades. Each pair of blades has a spar which extends from a first tip of a first one of the airfoil blades in the pair to a second tip of a second one of the airfoil blades in the pair. The rotor further comprises an outer shroud integrally joined to the first and second tips in each pair of airfoil blades and an inner diameter hub.