Is the inside of the mug stainless steel or plastic?

I purchased the coffee maker to help a disabled friend, who wanted your storage container and mug, which was on special as a gift if a person enrolled another.

I was unsuccessful in getting any of my friends or family to enroll due to the eocnomy. We love the coffee maker, and hopefully, we can get another person to enroll in your program next time you run the special. My disabled friend LOVES her storage container and mug.