An air displacement pipette

An air displacement pipette comprises a pipette tip mounting shaft and a disposable pipette tip having a proximal end mountable onto the tip mounting shaft and a distal sample receiving end. The shaft and tip are characterized by: the shaft having substantially cylindrical and axially spaced outer surface zones including an annular sealing zone and a lateral support zone, the tip having corresponding axially spaced inner regions including an annular sealing region and a lateral support region, and a sidewall in the annular sealing region of the tip being made annular and sufficiently thin that the sealing region expands slightly to form an interference fit and air tight seal between a sealing surface on an inner surface of the sidewall and the sealing zone of the shaft when the sealing zone penetrates the sealing region.