1. color will glow in the dark when you hold it for 15 minutes from the Bright Light, cool.2. Fluorescen String Length: 110 cm/ 43.3 inches, durable and lightweight, not easy to roll, .3. Yo-yo string should be changed periodically if yoyo string becomes defect.4. Best replacement string for responsive and unresponsvie yoyo.5. Fluorescen yo-yo strings made of premium Polyester fiber.colour: random colors, 't accept the specified colorMaterial: polyester fiberPackage Contents:25 x Yoyo StringsOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.