Light Up Toys Blue Flashing Yo Yo is a perfect party favor for the young at heart. Also makes for great stocking stuffers, light up gifts, and most excellent for school fundraisers. Light Up Toys Blue Flashing Yo Yo is a timeless classic with an LED modern twist! To activate the LED in your Blue Yo Yo Toy, just wind up the string and drop it! With every flick of the wrist, bright lights spin - so eye catching! Yo Yo must be in play for LEDs to light up. Dimensions: Diameter 2.25 in. LED Colors: Blue. Light Up Toys Blue Flashing Yo Yo comes ready to use with non-replaceable batteries.