Why the length of the string should between 30cm and 100cm?

The length of the string should be between 30 cm and 100 cm to ensure it is long enough for effective use while preventing excess slack that could lead to tangling or difficulty in handling. This range offers a balance between usability and practicality, making it suitable for various applications. Additionally, adhering to this length helps maintain safety standards, preventing potential hazards associated with overly long strings.