We have wanted to replace plastic storage containers with glass so were happy to see OXO come out with this line.  I have used the 3.5 cup container for leftovers and to bring my salad for lunch.  The top goes on and off easily and fits securely.   Washing is easy-I love that the seal can be removed for cleaning (and it slips back on easily.  Great product!  we will be buying more in other sizes