Power up the fun with “GraviTrax POWER Elements Starter and Finish” and automatically send a new ball down the track as each one finishes! Extend your marble run fun and launch a new ball down your track as one finishes — handsfree! Our “GraviTrax POWER Elements Starter and Finish” links the beginning and end of the track via radio (RF) signal. Load the Starter with up to 7 marbles. As a ball enters the Finish, it signals the Starter to launch a new one on its journey! How long can you race handsfree? An excellent addition to your existing GraviTrax system; completely compatible with GraviTrax products for tons of continuous fun! GraviTrax construction sets are a creative, expandable track system that challenges children to use their imagination to design and build their own marble runs! STEM-friendly concepts build critical thinking and problem-solving skills. Completely open-ended, every GraviTrax set has a boredom-busting variety of play options for hours of fascinating fun. Master the basics, then add expansion sets to propel those metal marbles around the tricked-out track of your dreams! Comes complete with instructions, 1 Starter, 1 Finish, 1 Finish-Arena. Requires 3 AAA batteries, not included. Lasting durability for girls and boys ages 8 and up; it's the learning toy children (and savvy adults) return to over and over again!