The cork band is a natural biodegradable product made from waste product of wine cork manufacture. Over time the cork may stain, giving your KeepCup a natural patina and well-loved look.
Cork lasts best with gentle hand-washing. Leave the cork band on the cup - do not remove it for general cleaning. Over time it will form a tight bond to the tumbler. Do not microwave KeepCup Brew Cork Edition, as this will accelerate the deterioration of the cork band by drying it out.