The tumbler is of decent quality. There are a few flaws with it that prevent me from giving it better than 3 stars. First is the venting system that doesn't seem to go anywhere. There is a hole going through the lid to the UNDERSIDE of the airproof slider. That is right. The vent doesn't vent anywhere meaning the liquid doesn't flow very well. I may take a red hot pin and vent it through the slider to correct. Issue two is that it is difficult to clean. Another reviewer mentioned you could pop off the slider to clean between the slider and the lid, but I'd be worried about breaking the slider after repeatedly popping it off. The final gripe, also mentioned by another reviewer, is that it isn't 20 ounces of usable space. If you fill to the top of the tumbler, you can get 20 ounces into the tumbler, but you can't get the lid on. Because the lid fits down inside the tumbler, you lose 4 ounces or so.Overall, the tumbler is good enough for the money, but I don't think I'd buy it again.
Rating: [5 of 5 Stars!]