I ordered a spare lid, hoping it would fit my existing tea mugs. It didn't quite, although I am keeping it because it works on some of my mugs. However, I called customer assistance to see if one of the other replacement lids might be a better fit. As a result of the call, I was sent a spare lid for free, and it fits perfectly! So I am really impressed with the customer service, and very happy that I now have plenty of lids to keep my mugs of tea warm. Thank you.