Bests & Worsts Reviews from Amazon

The reason it is not a 5 star review is due to the copper cup had a clear coating on the inside of the cup. It after several uses starts to scratch off. My guess is you are probably consuming part of the clear coating shavings since the added straws are solid copper and are the cause of some of the scrapes. Also, this coating on the inside is cup insulates the drink from the actual copper (the reason to have a copper cup) so the expected taste to the drink is not achieved. Copper increases the pH of the drink and allows for the TDS (total dissolved solids) to increase this changing the taste. You could just use steel wool and remove the coating from the inside but expect the copper to start to discolor from use. I have not done this yet.