1-Day Acuvue contact lenses come in boxes of 30 lenses. If you lose a lens you can use another from the same box. I don't know if you'd want to do it from a different box, though because for one, you have to make sure it's a box of lenses for the correct eye. Secondly, they should probably have the same lot number, although I don't think that's quite as important as making sure it's in the correct eye.