Summary I don't use a straw with my Ozark Trail branded 30 oz tumbler and I work in a warehouse so I wanted something to cover my cup so that dust or debris wouldn't fall into my cup. This cover prevents that. UPDATE 12-27-2016: Updated for improved fit and overall strength. You can now choose from a lid that is blank, reads Ozark or reads <3 - will make this customizable as soon as I figure out how to do that.