The cork band is a natural biodegradable product made from waste product of wine cork manufacture. The cork may stain, and we encourage you to view this as a natural patina to the product.
Do not microwave KeepCup Brew Cork Edition, it will accelerate the deterioration of the cork band by drying it out.
For longevity, we advise customers to hand wash only and to never remove the cork band, over time it will form a tight bond to the tumbler. For best results, leave the KeepCup Brew Cork Edition to dry prior to its next use.