Duncan Toys Yo-Yo String Assorted colors] - Pack of 5 cotton String for Plastic, Metal Yo-Yos Product Description Pack includes 5] yo-yo replacement strings in 5] different colors - Red, Orange, Yellow, green and Blue. This is the perfect replacement string for Duncan series of plastic and metal yo-yos. Easy to replace, this 5-pack of replacement cotton string is essential for yo-yo enthusiasts who often wear-out the string due to repeated usage. here are many types of yo-yo strings but the 100% cotton strings are considered the softest and have impressive resistance to wear & tear. cotton strings like these are least likely to burn or scrape-against the skin. From the Manufacturer 5-pack Multi-color replacement strings for all Duncan yo-yos. can be used with most yo-yos and are recommended to replace wornold yo-yo strings.