Walmart lid sucks I've read more than once. We have rtics and they beat the yetis at the lake and at my office, but not very scientific.
My RTIC 30oz lid is not as tight as my Yeti, but i'm still down two more RTICs. The RTIC lid is what I consider loose, while by Yeti lid is what I consider very tight.
My 20oz RTIC lid, despite a cosmetic blemish, fits tight on the appropriate cup.