These are the cardboard cores from rolls of plastic wrap. The length is approximately 30.6cm. There are 6 cores with an outer diameter of 37mm and an inner diameter of 34mm, and 2 cores with an outer diameter of 33mm and an inner diameter of 30mm, for a total of 8 cores. Due to the difference in diameter, they can be inserted into each other and slid, and can also be used in special ways by cutting them short and combining them. They are clean, with no stains or damage.