25 pre-sterilized storage bags. 6 oz (180 ml). 100% leak-proof double zipper, guaranteed! Improved oxygen barrier for freshness. Our strongest bag ever! BPA free. Trusted brand for 50+ years. Help us fight breast cancer. Each purchase supports a donation (Nuk will donate 1% of breastfeeding product sales thru Dec. 31, 2013 up to $80,000) to National Breast Cancer Foundation, Inc. Did you know? Breast feeding may reduce the risk of breast cancer - National Cancer Institute. For 50+ years, moms have trusted Nuk products to help them nurture their babies best. www.Nuk-USA.com. 100% leak proof - double zippers, extra wide seal. Freezer safe - improved oxygen barrier for freshness. Thick & durable - our strongest bag ever! Easy to store - self standing bag. Made in USA.