Bests & Worsts Reviews from Amazon

I really want to like this mug. I had the previous model and lost it. It liked it a lot. This one has the mouth piece redesigned a little bit. The problem I'm having is the rubber piece that closes the hole and the gasket that seals the threads impart a terrible chemical flavor to the coffee. Its hard to describe how bad it is. My wife confirmed it just by sniffing the cup. I tried soaking them in baking soda and water for a couple hours which didn't do much. I then tried soaking them in vinegar and it helped a little. Followed by a trip through the dishwasher. But the next day the problem was back. I emailed Stanley customer support with all this information and they just told me to read their FAQ which I already had - thus the vinegar and baking soda treatments. I really can't believe they would use such a bad rubber material in a drinking cup! So one star because of the bad material and because of the really poor customer service. I now need to see if there is a satisfaction guarantee - if so its definitely going back, its useless to me.