A package containing pre-packed yarn or cotton wool that is not an hermetically sealed package may be marked with the words "mass at standard condition" or with other words that have a similar meaning to those words if –

(a) the words are marked in the same way as the appropriate measurement marking; and

(b) when the yarn or cotton wool is composed of a mixture of fibres, the package is also marked in the same way as the appropriate measurement marking with a correct statement of the proportion by mass of each of the kinds of fibre of which the yarn or cotton wool is composed.