HERCULES cotton sash cord is manufactured from premium quality cotton yarn, without the cheap fillers common in so many commercially available sash cords. It is ideal as a general purpose cord where a natural fiber is required. 100% cotton, polished finish, non-rotating construction. This is the cord that will last decades, and it is made in America. The #8 is the standard size for ordinary size and weight window sashes. The #9 is for heavier sashes, especially those fitted with thick plate glass. Size is 1/4" diameter or 6.5 mm. 100 foot hank.