Knowledge of reflective yarn

Reflective yarn is a product cut with reflective cutting film, the size is between 0.3-5mm, the spool is fixed size, all reflective silk packaging is 20 rolls / box, the box size is also fixed 58 * 24 * 24.7 cm, only the corresponding size corresponds to the number of meters per roll, this should be determined by the supplier before the order to determine the number of meters per roll of the product, because the manufacturer's meter is not fixed.