Marbleocity Triple Play 4-Bar Link — Build A Wood Marble Machine — Tinkineer Stem Kit — For Ages 9+Build a model of four bar linkage! Use the hand crank or attach a motor (sold separately) to watch the marbles ascend and then flip flop down again! It's part of the first Marbleocity marble machine line to feature colorful plastic accents! Perfect for beginners; one hour build time. Triple Play models can connect to one another for bigger fun! Also works with Marbleocity Motor Kit, sold separately. For ages 9 and up.