Hummel Junior Gymnastics Slippers. The Hummel junior gym shoe is made of a soft material and has a durable, non-slip rubber sole. It has no laces; instead it has a herringbone elastic band for an easy fit while keeping your child's little feet in place. Features include flexible materials, a flexible and comfortable fit, and a durable, non-slip rubber outsole. The elastic band with chevrons ensures a secure fit.