Pipette tip couplers, pipette tips, coupler and tip combinations, and methods for coupling and decoupling a pipette tip to or from an expanding mandrel pipette tip coupler mounted on a pipette device. The pipette tip couplers include circumferentially spaced apart segments for engaging an interior surface of a pipette tip, an annular base disposed below the segments, a distal elastomeric element disposed around a distal stem portion for sealing against the interior surface of the pipette tip, upwardly extending circumferentially spaced apart arms each supporting a different segment, and a stop disk for abutting a stop shoulder in a pipette tip. The pipette tips include a groove in a first cylindrical section, a second cylindrical section, a pipette tip stop shoulder surface, a third cylindrical section, and a sealing seat surface.