Keep Calm Coffee Cup 5 "Love this mug" Deborah 13 December 2011 This is a great find for me. It is lovely to drink from, with or without the cover. The liquid keeps plenty warm enough for when I am out and about. Capacity is plenty. I have noted how to clean the top..Just not sure what the little stopper on the bottom is for!!! A note from the team Thanks for placing your review. The buyer has commented to say: Its a double wall cup.The stopper prevents heat loss through the base and also stops water getting between the 2 layers.