An air displacement pipette having axially spaced annular sealing and substantially cylindrical lateral support zones and regions on the pipette's mounting shaft and tip, respectively, in combination with means for insuring uniform depth of mounting shaft penetration into the pipette tip to maintain uniform tip interference with the mounting shaft as successive tips are mounted on and ejected from the mounting shaft whereby the pipette tip is easily and firmly mountable on and easily ejectable from the pipette tip mounting shaft by the application of axial mounting and ejection forces of about two pounds and one pound, respectively.