“THIS IS A MUST BUY!! the white tip goes on the straw, the bottom of the straw is flexible so you can push the straw down and close the hydrojug. I hit the top of mine to
make sure it is secure. Next time I open it up the straw tip pops right out and ready to drink. Spend the 5 it's beyond worth it. This is how you drink more water. If I had to pick up my jug to drink out of the hole, I wouldn't meet my water goals.”