I'm rating this product at five stars, because Amazon has combined reviews for at least five different products - and each one surely deserves at least one star.
Before you reply to, or accept any review for these products, know that the reviewer may be talking about a different product.
The only way you can be sure that the reviewer is talking about the same product is to click on the comment(s) link under the review, scroll to the top of the page, and look at the image on the upper right.
Thanks for breaking the reviewing system, Amazon. Looking at the one-star reviews, quite a number of them seem to be for the 21oz iced-tea glasses. So maybe the 9oz tumblers deserve a higher rating - but we'll never know, unless we click on each review to verify which product broke/didn't break/leaked, and tally the results ourselves.
Sort of defeats the purpose of a review system, doesn't it?