Happy owners of several nalgènes gourdes, I can only recommend this plug. As it simplifies its use in many ways. The small cap facilitates hydration (drinking to "bottle") and the color helps differentiate gourds when several in the same backpack, personally I have two, one with a green cap (which will to collect water in the river, for example) and the other with a blue cap (which will receive the purified water but never gets in contact with non-potable water)
