The Medela 8 oz Breastmilk Bottle Set is a safe plastic design for long-term breastmilk storage retains breastmilk's beneficial properties. It has a wide base and a medium-flow silicone nipple to complement breastfeeding. It has a colorful, easy to read volume marks in ounces and milliliters. They are also compatible with all Medela breastpumps. They are dishwasher and microwave safe. A convienent feature allows you to pump, store and feed with the same bottle.