I can't get the dropper top on my C15 Super Booster, Oil Booster, Hyaluronic Acid Booster, or Niacinamide Booster to screw on correctly. What's wrong?

Not a thing! These containers have an air restrictor insert that is attached on the dropper tube. This needs to be installed before using, and will keep the formula stable. The first time you insert and attempt to close the container it may feel as though it doesn't fit and it may appear crooked, but that's okay. Keep twisting while applying firm downwards pressure until you hear a click or snap. This confirms that the restrictor is installed properly, and you should be able to use the dropper top and reattach it as normal.