I would give this item 5 stars except that the lid no longer sits flush and always pops up a little. However even when that happens, it is still leak proof. It also took me two tries to install because when I put it on the first way (one side has a bit more of a lip to it) the lid was still leaking when I took a drink. After I switched it, the lid no longer leaks. I would still recommend this product for the price range.
Rating: [4 of 5 Stars!]