I use every day for ground French Roast and now have 4 broken caps for these cups.  I like not filling the landfill with plastic and enjoy fresh brewed dark roast, but each of the four caps have broken within weeks of daily use.  The wings of the cap are flimsy and get brittle very quickly and crack and break and I carefully hand wash them each day.  I now have 4 working bottom cups but no lids that are functional because of their poorly designed thin plastic top cap.  Should be stronger plastic or a metal top for durability.  I have super glue repaired each cap after they break but that only holds up for a few days before they crack/break again.  Now my 4 bottom cups are not usable.      .