I've read reviews about the cups being misshapen and damaged due to heat and sterilizing. Alot of the moms choose to discard the cups just to be safe. I would to, but I've always been paranoid about these things.
http://www.amazon.com/Philips-AVENT-Breast-Storage-10/product-reviews/B00PF841GQ?filterByStar=two_star&reviewerType=avp_only_reviews
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