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 100% Polyester fiber. colour: random colors, 't accept the specified color Material: polyester fiber Package Contents: 25 x Yoyo Strings Only 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.