Available sizes: 3.5,4,6. Puma Shoes (Trainers) Graviton Jr Available in boy's sizes. by Puma. Puma stands out with its famous Graviton Jr, low shoes with serious fashion credentials. As a brand that has a lot on its plate when it comes to trainers, it is taking advantage of this opportunity to bring together all the elements that have made it such a success. With a synthetic lining, little ones will love wearing the Graviton Jr day and night. Do you dare try out this pair of trainers that defy the odds? How can you resist this stylish pair?!