To accommodate the needs of more mothers, Medela has developed this customized system. Unique 2-piece system allows moms to choose breastshield size for maximum personal comfort while pumping. Works with all Medela® breastpumps except disposable kits. Attaches to all Medela standard breast pumps. Large 27mm (for reference, the 24mm is included in Medela"s breastpump kits). Pack of 2.Safe for baby - All parts that come into contact with breastmilk are BPA/DEHP Free.