Stacking fun has never been so much fun! Three big train cars are the ideal size for baby to grab and carry, as well as stack, nest, and attach. Stacking the cars in order of scale or nesting them one inside the other lets the kid appreciate size relationships and how objects work together. To promote pressing and crawling, roll them along. Three big train cars are the best size for a baby to catch and carry. Connecting the train cars also assists in the growth of baby's eye-hand coordination. ? Connectable rail cars with rolling wheels enable baby to drive the train and crawl around, allowing him to practise gross motor skills.