Love these! So easy to keep clean, the vehicles are easily removed on the bottom to throw in the washing machine! Wheel them back to get new skills speeding ahead! The "rev up" mechanism inside each of these four cars and trucks makes it easy for babies and toddlers to get big acceleration with just a little input: Pull back one of the soft vehicles--then release to see it zoom off across the floor! The action of grasping and pulling back is great for fine motor skills and hand-eye coordination; the activity of "driving" and collecting (pull, release, crawl) benefits large muscle groups and coordination, too.